diff --git a/telethon/client/telegrambaseclient.py b/telethon/client/telegrambaseclient.py
index d764c99c..48eba037 100644
--- a/telethon/client/telegrambaseclient.py
+++ b/telethon/client/telegrambaseclient.py
@@ -10,7 +10,6 @@ import datetime
 
 from .. import version, helpers, __name__ as __base_name__
 from ..crypto import rsa
-from ..entitycache import EntityCache
 from ..extensions import markdown
 from ..network import MTProtoSender, Connection, ConnectionTcpFull, TcpMTProxy
 from ..sessions import Session, SQLiteSession, MemorySession
diff --git a/telethon/entitycache.py b/telethon/entitycache.py
deleted file mode 100644
index b6d06b3c..00000000
--- a/telethon/entitycache.py
+++ /dev/null
@@ -1,147 +0,0 @@
-import inspect
-import itertools
-
-from . import utils
-from .tl import types
-
-# Which updates have the following fields?
-_has_field = {
-    ('user_id', int): [],
-    ('chat_id', int): [],
-    ('channel_id', int): [],
-    ('peer', 'TypePeer'): [],
-    ('peer', 'TypeDialogPeer'): [],
-    ('message', 'TypeMessage'): [],
-}
-
-# Note: We don't bother checking for some rare:
-# * `UpdateChatParticipantAdd.inviter_id` integer.
-# * `UpdateNotifySettings.peer` dialog peer.
-# * `UpdatePinnedDialogs.order` list of dialog peers.
-# * `UpdateReadMessagesContents.messages` list of messages.
-# * `UpdateChatParticipants.participants` list of participants.
-#
-# There are also some uninteresting `update.message` of type string.
-
-
-def _fill():
-    for name in dir(types):
-        update = getattr(types, name)
-        if getattr(update, 'SUBCLASS_OF_ID', None) == 0x9f89304e:
-            cid = update.CONSTRUCTOR_ID
-            sig = inspect.signature(update.__init__)
-            for param in sig.parameters.values():
-                vec = _has_field.get((param.name, param.annotation))
-                if vec is not None:
-                    vec.append(cid)
-
-    # Future-proof check: if the documentation format ever changes
-    # then we won't be able to pick the update types we are interested
-    # in, so we must make sure we have at least an update for each field
-    # which likely means we are doing it right.
-    if not all(_has_field.values()):
-        raise RuntimeError('FIXME: Did the init signature or updates change?')
-
-
-# We use a function to avoid cluttering the globals (with name/update/cid/doc)
-_fill()
-
-
-class EntityCache:
-    """
-    In-memory input entity cache, defaultdict-like behaviour.
-    """
-    def add(self, entities):
-        """
-        Adds the given entities to the cache, if they weren't saved before.
-        """
-        if not utils.is_list_like(entities):
-            # Invariant: all "chats" and "users" are always iterables,
-            # and "user" never is (so we wrap it inside a list).
-            entities = itertools.chain(
-                getattr(entities, 'chats', []),
-                getattr(entities, 'users', []),
-                (hasattr(entities, 'user') and [entities.user]) or []
-            )
-
-        for entity in entities:
-            try:
-                pid = utils.get_peer_id(entity)
-                if pid not in self.__dict__:
-                    # Note: `get_input_peer` already checks for `access_hash`
-                    self.__dict__[pid] = utils.get_input_peer(entity)
-            except TypeError:
-                pass
-
-    def __getitem__(self, item):
-        """
-        Gets the corresponding :tl:`InputPeer` for the given ID or peer,
-        or raises ``KeyError`` on any error (i.e. cannot be found).
-        """
-        if not isinstance(item, int) or item < 0:
-            try:
-                return self.__dict__[utils.get_peer_id(item)]
-            except TypeError:
-                raise KeyError('Invalid key will not have entity') from None
-
-        for cls in (types.PeerUser, types.PeerChat, types.PeerChannel):
-            result = self.__dict__.get(utils.get_peer_id(cls(item)))
-            if result:
-                return result
-
-        raise KeyError('No cached entity for the given key')
-
-    def clear(self):
-        """
-        Clear the entity cache.
-        """
-        self.__dict__.clear()
-
-    def ensure_cached(
-            self,
-            update,
-            has_user_id=frozenset(_has_field[('user_id', int)]),
-            has_chat_id=frozenset(_has_field[('chat_id', int)]),
-            has_channel_id=frozenset(_has_field[('channel_id', int)]),
-            has_peer=frozenset(_has_field[('peer', 'TypePeer')] + _has_field[('peer', 'TypeDialogPeer')]),
-            has_message=frozenset(_has_field[('message', 'TypeMessage')])
-    ):
-        """
-        Ensures that all the relevant entities in the given update are cached.
-        """
-        # This method is called pretty often and we want it to have the lowest
-        # overhead possible. For that, we avoid `isinstance` and constantly
-        # getting attributes out of `types.` by "caching" the constructor IDs
-        # in sets inside the arguments, and using local variables.
-        dct = self.__dict__
-        cid = update.CONSTRUCTOR_ID
-        if cid in has_user_id and \
-                update.user_id not in dct:
-            return False
-
-        if cid in has_chat_id and \
-                utils.get_peer_id(types.PeerChat(update.chat_id)) not in dct:
-            return False
-
-        if cid in has_channel_id and \
-                utils.get_peer_id(types.PeerChannel(update.channel_id)) not in dct:
-            return False
-
-        if cid in has_peer and \
-                utils.get_peer_id(update.peer) not in dct:
-            return False
-
-        if cid in has_message:
-            x = update.message
-            y = getattr(x, 'peer_id', None)  # handle MessageEmpty
-            if y and utils.get_peer_id(y) not in dct:
-                return False
-
-            y = getattr(x, 'from_id', None)
-            if y and utils.get_peer_id(y) not in dct:
-                return False
-
-            # We don't quite worry about entities anywhere else.
-            # This is enough.
-
-        return True