diff --git a/rest_framework/authentication.py b/rest_framework/authentication.py
index 124ef68ac..7e86a7b9f 100644
--- a/rest_framework/authentication.py
+++ b/rest_framework/authentication.py
@@ -5,6 +5,7 @@ from __future__ import unicode_literals
 import base64
 from django.contrib.auth import authenticate
 from django.middleware.csrf import CsrfViewMiddleware
+from django.utils.translation import ugettext_lazy as _
 from rest_framework import exceptions, HTTP_HEADER_ENCODING
 from rest_framework.authtoken.models import Token
 
@@ -65,16 +66,16 @@ class BasicAuthentication(BaseAuthentication):
             return None
 
         if len(auth) == 1:
-            msg = 'Invalid basic header. No credentials provided.'
+            msg = _("Invalid basic header. No credentials provided.")
             raise exceptions.AuthenticationFailed(msg)
         elif len(auth) > 2:
-            msg = 'Invalid basic header. Credentials string should not contain spaces.'
+            msg = _("Invalid basic header. Credentials string should not contain spaces.")
             raise exceptions.AuthenticationFailed(msg)
 
         try:
             auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
         except (TypeError, UnicodeDecodeError):
-            msg = 'Invalid basic header. Credentials not correctly base64 encoded'
+            msg = _("Invalid basic header. Credentials not correctly base64 encoded.")
             raise exceptions.AuthenticationFailed(msg)
 
         userid, password = auth_parts[0], auth_parts[2]
@@ -86,7 +87,7 @@ class BasicAuthentication(BaseAuthentication):
         """
         user = authenticate(username=userid, password=password)
         if user is None or not user.is_active:
-            raise exceptions.AuthenticationFailed('Invalid username/password')
+            raise exceptions.AuthenticationFailed(_("Invalid username/password."))
         return (user, None)
 
     def authenticate_header(self, request):
@@ -152,10 +153,10 @@ class TokenAuthentication(BaseAuthentication):
             return None
 
         if len(auth) == 1:
-            msg = 'Invalid token header. No credentials provided.'
+            msg = _("Invalid token header. No credentials provided.")
             raise exceptions.AuthenticationFailed(msg)
         elif len(auth) > 2:
-            msg = 'Invalid token header. Token string should not contain spaces.'
+            msg = _("Invalid token header. Token string should not contain spaces.")
             raise exceptions.AuthenticationFailed(msg)
 
         return self.authenticate_credentials(auth[1])
@@ -164,10 +165,10 @@ class TokenAuthentication(BaseAuthentication):
         try:
             token = self.model.objects.get(key=key)
         except self.model.DoesNotExist:
-            raise exceptions.AuthenticationFailed('Invalid token')
+            raise exceptions.AuthenticationFailed(_("Invalid token"))
 
         if not token.user.is_active:
-            raise exceptions.AuthenticationFailed('User inactive or deleted')
+            raise exceptions.AuthenticationFailed(_("User inactive or deleted"))
 
         return (token.user, token)
 
diff --git a/rest_framework/authtoken/serializers.py b/rest_framework/authtoken/serializers.py
index f31dded17..78fe6a117 100644
--- a/rest_framework/authtoken/serializers.py
+++ b/rest_framework/authtoken/serializers.py
@@ -17,13 +17,13 @@ class AuthTokenSerializer(serializers.Serializer):
 
             if user:
                 if not user.is_active:
-                    msg = _('User account is disabled.')
+                    msg = _("User account is disabled.")
                     raise exceptions.ValidationError(msg)
             else:
-                msg = _('Unable to log in with provided credentials.')
+                msg = _("Unable to log in with provided credentials.")
                 raise exceptions.ValidationError(msg)
         else:
-            msg = _('Must include "username" and "password"')
+            msg = _("Must include \"username\" and \"password\"")
             raise exceptions.ValidationError(msg)
 
         attrs['user'] = user
diff --git a/rest_framework/exceptions.py b/rest_framework/exceptions.py
index dfc57293e..3ca8e5380 100644
--- a/rest_framework/exceptions.py
+++ b/rest_framework/exceptions.py
@@ -35,7 +35,7 @@ class APIException(Exception):
     Subclasses should provide `.status_code` and `.default_detail` properties.
     """
     status_code = status.HTTP_500_INTERNAL_SERVER_ERROR
-    default_detail = _('A server error occurred.')
+    default_detail = _("A server error occurred.")
 
     def __init__(self, detail=None):
         if detail is not None:
@@ -52,7 +52,7 @@ class APIException(Exception):
 # built in `ValidationError`. For example:
 #
 # from rest_framework import serializers
-# raise serializers.ValidationError('Value was invalid')
+# raise serializers.ValidationError("Value was invalid")
 
 class ValidationError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
@@ -70,32 +70,32 @@ class ValidationError(APIException):
 
 class ParseError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
-    default_detail = _('Malformed request.')
+    default_detail = _("Malformed request.")
 
 
 class AuthenticationFailed(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
-    default_detail = _('Incorrect authentication credentials.')
+    default_detail = _("Incorrect authentication credentials.")
 
 
 class NotAuthenticated(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
-    default_detail = _('Authentication credentials were not provided.')
+    default_detail = _("Authentication credentials were not provided.")
 
 
 class PermissionDenied(APIException):
     status_code = status.HTTP_403_FORBIDDEN
-    default_detail = _('You do not have permission to perform this action.')
+    default_detail = _("You do not have permission to perform this action.")
 
 
 class NotFound(APIException):
     status_code = status.HTTP_404_NOT_FOUND
-    default_detail = _('Not found.')
+    default_detail = _("Not found.")
 
 
 class MethodNotAllowed(APIException):
     status_code = status.HTTP_405_METHOD_NOT_ALLOWED
-    default_detail = _("Method {method} not allowed.")
+    default_detail = _("Method '{method}' not allowed.")
 
     def __init__(self, method, detail=None):
         if detail is not None:
@@ -106,7 +106,7 @@ class MethodNotAllowed(APIException):
 
 class NotAcceptable(APIException):
     status_code = status.HTTP_406_NOT_ACCEPTABLE
-    default_detail = _('Could not satisfy the request Accept header.')
+    default_detail = _("Could not satisfy the request Accept header.")
 
     def __init__(self, detail=None, available_renderers=None):
         if detail is not None:
@@ -131,9 +131,9 @@ class UnsupportedMediaType(APIException):
 
 class Throttled(APIException):
     status_code = status.HTTP_429_TOO_MANY_REQUESTS
-    default_detail = _('Request was throttled.')
-    extra_detail_singular = 'Expected available in {wait} second.'
-    extra_detail_plural = 'Expected available in {wait} seconds.'
+    default_detail = _("Request was throttled.")
+    extra_detail_singular = "Expected available in {wait} second."
+    extra_detail_plural = "Expected available in {wait} seconds."
 
     def __init__(self, wait=None, detail=None):
         if detail is not None:
diff --git a/rest_framework/fields.py b/rest_framework/fields.py
index 0ff2b0733..8a781b356 100644
--- a/rest_framework/fields.py
+++ b/rest_framework/fields.py
@@ -149,8 +149,8 @@ class Field(object):
     _creation_counter = 0
 
     default_error_messages = {
-        'required': _('This field is required.'),
-        'null': _('This field may not be null.')
+        'required': _("This field is required."),
+        'null': _("This field may not be null.")
     }
     default_validators = []
     default_empty_html = empty
@@ -477,7 +477,7 @@ class Field(object):
 
 class BooleanField(Field):
     default_error_messages = {
-        'invalid': _('`{input}` is not a valid boolean.')
+        'invalid': _("`{input}` is not a valid boolean.")
     }
     default_empty_html = False
     initial = False
@@ -505,7 +505,7 @@ class BooleanField(Field):
 
 class NullBooleanField(Field):
     default_error_messages = {
-        'invalid': _('`{input}` is not a valid boolean.')
+        'invalid': _("`{input}` is not a valid boolean.")
     }
     initial = None
     TRUE_VALUES = set(('t', 'T', 'true', 'True', 'TRUE', '1', 1, True))
@@ -540,9 +540,9 @@ class NullBooleanField(Field):
 
 class CharField(Field):
     default_error_messages = {
-        'blank': _('This field may not be blank.'),
-        'max_length': _('Ensure this field has no more than {max_length} characters.'),
-        'min_length': _('Ensure this field has at least {min_length} characters.')
+        'blank': _("This field may not be blank."),
+        'max_length': _("Ensure this field has no more than {max_length} characters."),
+        'min_length': _("Ensure this field has at least {min_length} characters.")
     }
     initial = ''
     coerce_blank_to_null = False
@@ -584,7 +584,7 @@ class CharField(Field):
 
 class EmailField(CharField):
     default_error_messages = {
-        'invalid': _('Enter a valid email address.')
+        'invalid': _("Enter a valid email address.")
     }
 
     def __init__(self, **kwargs):
@@ -601,7 +601,7 @@ class EmailField(CharField):
 
 class RegexField(CharField):
     default_error_messages = {
-        'invalid': _('This value does not match the required pattern.')
+        'invalid': _("This value does not match the required pattern.")
     }
 
     def __init__(self, regex, **kwargs):
@@ -637,10 +637,10 @@ class URLField(CharField):
 
 class IntegerField(Field):
     default_error_messages = {
-        'invalid': _('A valid integer is required.'),
-        'max_value': _('Ensure this value is less than or equal to {max_value}.'),
-        'min_value': _('Ensure this value is greater than or equal to {min_value}.'),
-        'max_string_length': _('String value too large.')
+        'invalid': _("A valid integer is required."),
+        'max_value': _("Ensure this value is less than or equal to {max_value}."),
+        'min_value': _("Ensure this value is greater than or equal to {min_value}."),
+        'max_string_length': _("String value too large.")
     }
     MAX_STRING_LENGTH = 1000  # Guard against malicious string inputs.
 
@@ -672,9 +672,9 @@ class IntegerField(Field):
 class FloatField(Field):
     default_error_messages = {
         'invalid': _("A valid number is required."),
-        'max_value': _('Ensure this value is less than or equal to {max_value}.'),
-        'min_value': _('Ensure this value is greater than or equal to {min_value}.'),
-        'max_string_length': _('String value too large.')
+        'max_value': _("Ensure this value is less than or equal to {max_value}."),
+        'min_value': _("Ensure this value is greater than or equal to {min_value}."),
+        'max_string_length': _("String value too large.")
     }
     MAX_STRING_LENGTH = 1000  # Guard against malicious string inputs.
 
@@ -704,13 +704,13 @@ class FloatField(Field):
 
 class DecimalField(Field):
     default_error_messages = {
-        'invalid': _('A valid number is required.'),
-        'max_value': _('Ensure this value is less than or equal to {max_value}.'),
-        'min_value': _('Ensure this value is greater than or equal to {min_value}.'),
-        'max_digits': _('Ensure that there are no more than {max_digits} digits in total.'),
-        'max_decimal_places': _('Ensure that there are no more than {max_decimal_places} decimal places.'),
-        'max_whole_digits': _('Ensure that there are no more than {max_whole_digits} digits before the decimal point.'),
-        'max_string_length': _('String value too large.')
+        'invalid': _("A valid number is required."),
+        'max_value': _("Ensure this value is less than or equal to {max_value}."),
+        'min_value': _("Ensure this value is greater than or equal to {min_value}."),
+        'max_digits': _("Ensure that there are no more than {max_digits} digits in total."),
+        'max_decimal_places': _("Ensure that there are no more than {max_decimal_places} decimal places."),
+        'max_whole_digits': _("Ensure that there are no more than {max_whole_digits} digits before the decimal point."),
+        'max_string_length': _("String value too large.")
     }
     MAX_STRING_LENGTH = 1000  # Guard against malicious string inputs.
 
@@ -793,8 +793,8 @@ class DecimalField(Field):
 
 class DateTimeField(Field):
     default_error_messages = {
-        'invalid': _('Datetime has wrong format. Use one of these formats instead: {format}.'),
-        'date': _('Expected a datetime but got a date.'),
+        'invalid': _("Datetime has wrong format. Use one of these formats instead: {format}."),
+        'date': _("Expected a datetime but got a date."),
     }
     format = api_settings.DATETIME_FORMAT
     input_formats = api_settings.DATETIME_INPUT_FORMATS
@@ -858,8 +858,8 @@ class DateTimeField(Field):
 
 class DateField(Field):
     default_error_messages = {
-        'invalid': _('Date has wrong format. Use one of these formats instead: {format}.'),
-        'datetime': _('Expected a date but got a datetime.'),
+        'invalid': _("Date has wrong format. Use one of these formats instead: {format}."),
+        'datetime': _("Expected a date but got a datetime."),
     }
     format = api_settings.DATE_FORMAT
     input_formats = api_settings.DATE_INPUT_FORMATS
@@ -916,7 +916,7 @@ class DateField(Field):
 
 class TimeField(Field):
     default_error_messages = {
-        'invalid': _('Time has wrong format. Use one of these formats instead: {format}.'),
+        'invalid': _("Time has wrong format. Use one of these formats instead: {format}."),
     }
     format = api_settings.TIME_FORMAT
     input_formats = api_settings.TIME_INPUT_FORMATS
@@ -972,7 +972,7 @@ class TimeField(Field):
 
 class ChoiceField(Field):
     default_error_messages = {
-        'invalid_choice': _('`{input}` is not a valid choice.')
+        'invalid_choice': _("`{input}` is not a valid choice.")
     }
 
     def __init__(self, choices, **kwargs):
@@ -1016,8 +1016,8 @@ class ChoiceField(Field):
 
 class MultipleChoiceField(ChoiceField):
     default_error_messages = {
-        'invalid_choice': _('`{input}` is not a valid choice.'),
-        'not_a_list': _('Expected a list of items but got type `{input_type}`.')
+        'invalid_choice': _("`{input}` is not a valid choice."),
+        'not_a_list': _("Expected a list of items but got type `{input_type}`.")
     }
     default_empty_html = []
 
@@ -1051,7 +1051,7 @@ class FileField(Field):
         'invalid': _("The submitted data was not a file. Check the encoding type on the form."),
         'no_name': _("No filename could be determined."),
         'empty': _("The submitted file is empty."),
-        'max_length': _('Ensure this filename has at most {max_length} characters (it has {length}).'),
+        'max_length': _("Ensure this filename has at most {max_length} characters (it has {length})."),
     }
     use_url = api_settings.UPLOADED_FILES_USE_URL
 
@@ -1118,7 +1118,7 @@ class ListField(Field):
     child = None
     initial = []
     default_error_messages = {
-        'not_a_list': _('Expected a list of items but got type `{input_type}`.')
+        'not_a_list': _("Expected a list of items but got type `{input_type}`.")
     }
 
     def __init__(self, *args, **kwargs):
@@ -1249,7 +1249,7 @@ class ModelField(Field):
     that do not have a serializer field to be mapped to.
     """
     default_error_messages = {
-        'max_length': _('Ensure this field has no more than {max_length} characters.'),
+        'max_length': _("Ensure this field has no more than {max_length} characters."),
     }
 
     def __init__(self, model_field, **kwargs):
diff --git a/rest_framework/generics.py b/rest_framework/generics.py
index 7c4d5e958..c7053d8f3 100644
--- a/rest_framework/generics.py
+++ b/rest_framework/generics.py
@@ -125,7 +125,7 @@ class GenericAPIView(views.APIView):
         try:
             page = paginator.page(page_number)
         except InvalidPage as exc:
-            error_format = _('Invalid page ({page_number}): {message}')
+            error_format = _("Invalid page ({page_number}): {message}.")
             raise NotFound(error_format.format(
                 page_number=page_number, message=six.text_type(exc)
             ))
diff --git a/rest_framework/relations.py b/rest_framework/relations.py
index 7b119291d..3737b21fa 100644
--- a/rest_framework/relations.py
+++ b/rest_framework/relations.py
@@ -128,9 +128,9 @@ class StringRelatedField(RelatedField):
 
 class PrimaryKeyRelatedField(RelatedField):
     default_error_messages = {
-        'required': _('This field is required.'),
+        'required': _("This field is required."),
         'does_not_exist': _("Invalid pk '{pk_value}' - object does not exist."),
-        'incorrect_type': _('Incorrect type. Expected pk value, received {data_type}.'),
+        'incorrect_type': _("Incorrect type. Expected pk value, received {data_type}."),
     }
 
     def use_pk_only_optimization(self):
@@ -152,11 +152,11 @@ class HyperlinkedRelatedField(RelatedField):
     lookup_field = 'pk'
 
     default_error_messages = {
-        'required': _('This field is required.'),
-        'no_match': _('Invalid hyperlink - No URL match'),
-        'incorrect_match': _('Invalid hyperlink - Incorrect URL match.'),
-        'does_not_exist': _('Invalid hyperlink - Object does not exist.'),
-        'incorrect_type': _('Incorrect type. Expected URL string, received {data_type}.'),
+        'required': _("This field is required."),
+        'no_match': _("Invalid hyperlink - No URL match."),
+        'incorrect_match': _("Invalid hyperlink - Incorrect URL match."),
+        'does_not_exist': _("Invalid hyperlink - Object does not exist."),
+        'incorrect_type': _("Incorrect type. Expected URL string, received {data_type}."),
     }
 
     def __init__(self, view_name=None, **kwargs):
@@ -292,7 +292,7 @@ class SlugRelatedField(RelatedField):
 
     default_error_messages = {
         'does_not_exist': _("Object with {slug_name}={value} does not exist."),
-        'invalid': _('Invalid value.'),
+        'invalid': _("Invalid value."),
     }
 
     def __init__(self, slug_field=None, **kwargs):
diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 623ed5865..9d7c8884a 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -296,7 +296,7 @@ def get_validation_error_detail(exc):
 @six.add_metaclass(SerializerMetaclass)
 class Serializer(BaseSerializer):
     default_error_messages = {
-        'invalid': _('Invalid data. Expected a dictionary, but got {datatype}.')
+        'invalid': _("Invalid data. Expected a dictionary, but got {datatype}.")
     }
 
     @property
@@ -473,7 +473,7 @@ class ListSerializer(BaseSerializer):
     many = True
 
     default_error_messages = {
-        'not_a_list': _('Expected a list of items but got type `{input_type}`.')
+        'not_a_list': _("Expected a list of items but got type `{input_type}`.")
     }
 
     def __init__(self, *args, **kwargs):
diff --git a/rest_framework/validators.py b/rest_framework/validators.py
index e3719b8d5..cf6f07180 100644
--- a/rest_framework/validators.py
+++ b/rest_framework/validators.py
@@ -19,7 +19,7 @@ class UniqueValidator:
 
     Should be applied to an individual field on the serializer.
     """
-    message = _('This field must be unique.')
+    message = _("This field must be unique.")
 
     def __init__(self, queryset, message=None):
         self.queryset = queryset
@@ -73,8 +73,8 @@ class UniqueTogetherValidator:
 
     Should be applied to the serializer class, not to an individual field.
     """
-    message = _('The fields {field_names} must make a unique set.')
-    missing_message = _('This field is required.')
+    message = _("The fields {field_names} must make a unique set.")
+    missing_message = _("This field is required.")
 
     def __init__(self, queryset, fields, message=None):
         self.queryset = queryset
@@ -152,7 +152,7 @@ class UniqueTogetherValidator:
 
 class BaseUniqueForValidator:
     message = None
-    missing_message = _('This field is required.')
+    missing_message = _("This field is required.")
 
     def __init__(self, queryset, field, date_field, message=None):
         self.queryset = queryset
@@ -216,7 +216,7 @@ class BaseUniqueForValidator:
 
 
 class UniqueForDateValidator(BaseUniqueForValidator):
-    message = _('This field must be unique for the "{date_field}" date.')
+    message = _("This field must be unique for the \"{date_field}\" date.")
 
     def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
@@ -231,7 +231,7 @@ class UniqueForDateValidator(BaseUniqueForValidator):
 
 
 class UniqueForMonthValidator(BaseUniqueForValidator):
-    message = _('This field must be unique for the "{date_field}" month.')
+    message = _("This field must be unique for the \"{date_field}\" month.")
 
     def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
@@ -244,7 +244,7 @@ class UniqueForMonthValidator(BaseUniqueForValidator):
 
 
 class UniqueForYearValidator(BaseUniqueForValidator):
-    message = _('This field must be unique for the "{date_field}" year.')
+    message = _("This field must be unique for the \"{date_field}\" year.")
 
     def filter_queryset(self, attrs, queryset):
         value = attrs[self.field]
diff --git a/rest_framework/versioning.py b/rest_framework/versioning.py
index 440efd139..587ba9f13 100644
--- a/rest_framework/versioning.py
+++ b/rest_framework/versioning.py
@@ -67,7 +67,7 @@ class URLPathVersioning(BaseVersioning):
     Host: example.com
     Accept: application/json
     """
-    invalid_version_message = _('Invalid version in URL path.')
+    invalid_version_message = _("Invalid version in URL path.")
 
     def determine_version(self, request, *args, **kwargs):
         version = kwargs.get(self.version_param, self.default_version)
@@ -109,7 +109,7 @@ class NamespaceVersioning(BaseVersioning):
     Host: example.com
     Accept: application/json
     """
-    invalid_version_message = _('Invalid version in URL path.')
+    invalid_version_message = _("Invalid version in URL path.")
 
     def determine_version(self, request, *args, **kwargs):
         resolver_match = getattr(request, 'resolver_match', None)
@@ -135,7 +135,7 @@ class HostNameVersioning(BaseVersioning):
     Accept: application/json
     """
     hostname_regex = re.compile(r'^([a-zA-Z0-9]+)\.[a-zA-Z0-9]+\.[a-zA-Z0-9]+$')
-    invalid_version_message = _('Invalid version in hostname.')
+    invalid_version_message = _("Invalid version in hostname.")
 
     def determine_version(self, request, *args, **kwargs):
         hostname, seperator, port = request.get_host().partition(':')
@@ -157,7 +157,7 @@ class QueryParameterVersioning(BaseVersioning):
     Host: example.com
     Accept: application/json
     """
-    invalid_version_message = _('Invalid version in query parameter.')
+    invalid_version_message = _("Invalid version in query parameter.")
 
     def determine_version(self, request, *args, **kwargs):
         version = request.query_params.get(self.version_param)