diff --git a/doc/extdev/appapi.rst b/doc/extdev/appapi.rst
index 4cb8501be..18eea34e7 100644
--- a/doc/extdev/appapi.rst
+++ b/doc/extdev/appapi.rst
@@ -145,7 +145,7 @@ Sphinx core events
 ------------------
 
 These events are known to the core.  The arguments shown are given to the
-registered event handlers.  Use :meth:`.connect` in an extension's ``setup``
+registered event handlers.  Use :meth:`.Sphinx.connect` in an extension's ``setup``
 function (note that ``conf.py`` can also have a ``setup`` function) to connect
 handlers to the events.  Example:
 
diff --git a/doc/extdev/builderapi.rst b/doc/extdev/builderapi.rst
index 2c2cf12e3..0ab7a30f4 100644
--- a/doc/extdev/builderapi.rst
+++ b/doc/extdev/builderapi.rst
@@ -38,3 +38,8 @@ Builder API
    .. automethod:: write_doc
    .. automethod:: finish
 
+   **Attributes**
+
+   .. attribute:: events
+
+      An :class:`.EventManager` object.
diff --git a/doc/extdev/envapi.rst b/doc/extdev/envapi.rst
index 1dee6a576..d7ec23925 100644
--- a/doc/extdev/envapi.rst
+++ b/doc/extdev/envapi.rst
@@ -27,6 +27,10 @@ Build environment API
 
       Directory for storing pickled doctrees.
 
+   .. attribute:: events
+
+      An :class:`.EventManager` object.
+
    .. attribute:: found_docs
 
       A set of all existing docnames.
diff --git a/doc/extdev/utils.rst b/doc/extdev/utils.rst
index 2a94a34bb..e842f3032 100644
--- a/doc/extdev/utils.rst
+++ b/doc/extdev/utils.rst
@@ -29,3 +29,9 @@ components (e.g. :class:`.Config`, :class:`.BuildEnvironment` and so on) easily.
 
 .. autoclass:: sphinx.transforms.post_transforms.images.ImageConverter
    :members:
+
+Utility components
+------------------
+
+.. autoclass:: sphinx.events.EventManager
+   :members:
diff --git a/sphinx/application.py b/sphinx/application.py
index afcdc02ed..e9b950c83 100644
--- a/sphinx/application.py
+++ b/sphinx/application.py
@@ -182,7 +182,7 @@ class Sphinx:
             self.warningiserror = warningiserror
         logging.setup(self, self._status, self._warning)
 
-        self.events = EventManager()
+        self.events = EventManager(self)
 
         # keep last few messages for traceback
         # This will be filled by sphinx.util.logging.LastMessagesWriter
@@ -249,7 +249,7 @@ class Sphinx:
 
         # now that we know all config values, collect them from conf.py
         self.config.init_values()
-        self.emit('config-inited', self.config)
+        self.events.emit('config-inited', self.config)
 
         # create the project
         self.project = Project(self.srcdir, self.config.source_suffix)
@@ -319,7 +319,7 @@ class Sphinx:
         # type: () -> None
         self.builder.set_environment(self.env)
         self.builder.init()
-        self.emit('builder-inited')
+        self.events.emit('builder-inited')
 
     # ---- main "build" method -------------------------------------------------
 
@@ -360,10 +360,10 @@ class Sphinx:
             envfile = path.join(self.doctreedir, ENV_PICKLE_FILENAME)
             if path.isfile(envfile):
                 os.unlink(envfile)
-            self.emit('build-finished', err)
+            self.events.emit('build-finished', err)
             raise
         else:
-            self.emit('build-finished', None)
+            self.events.emit('build-finished', None)
         self.builder.cleanup()
 
     # ---- general extensibility interface -------------------------------------
@@ -420,13 +420,7 @@ class Sphinx:
         Return the return values of all callbacks as a list.  Do not emit core
         Sphinx events in extensions!
         """
-        try:
-            logger.debug('[app] emitting event: %r%s', event, repr(args)[:100])
-        except Exception:
-            # not every object likes to be repr()'d (think
-            # random stuff coming via autodoc)
-            pass
-        return self.events.emit(event, self, *args)
+        return self.events.emit(event, *args)
 
     def emit_firstresult(self, event, *args):
         # type: (str, Any) -> Any
@@ -436,7 +430,7 @@ class Sphinx:
 
         .. versionadded:: 0.5
         """
-        return self.events.emit_firstresult(event, self, *args)
+        return self.events.emit_firstresult(event, *args)
 
     # registering addon parts
 
diff --git a/sphinx/builders/__init__.py b/sphinx/builders/__init__.py
index 1b29fa983..8eaa0e215 100644
--- a/sphinx/builders/__init__.py
+++ b/sphinx/builders/__init__.py
@@ -43,6 +43,7 @@ if False:
     from sphinx.application import Sphinx  # NOQA
     from sphinx.config import Config  # NOQA
     from sphinx.environment import BuildEnvironment  # NOQA
+    from sphinx.events import EventManager  # NOQA
     from sphinx.util.i18n import CatalogInfo  # NOQA
     from sphinx.util.tags import Tags  # NOQA
 
@@ -93,6 +94,7 @@ class Builder:
 
         self.app = app              # type: Sphinx
         self.env = None             # type: BuildEnvironment
+        self.events = app.events    # type: EventManager
         self.config = app.config    # type: Config
         self.tags = app.tags        # type: Tags
         self.tags.add(self.format)
@@ -399,7 +401,7 @@ class Builder:
         added, changed, removed = self.env.get_outdated_files(updated)
 
         # allow user intervention as well
-        for docs in self.app.emit('env-get-outdated', self, added, changed, removed):
+        for docs in self.events.emit('env-get-outdated', self, added, changed, removed):
             changed.update(set(docs) & self.env.found_docs)
 
         # if files were added or removed, all documents with globbed toctrees
@@ -416,13 +418,13 @@ class Builder:
 
         # clear all files no longer present
         for docname in removed:
-            self.app.emit('env-purge-doc', self.env, docname)
+            self.events.emit('env-purge-doc', self.env, docname)
             self.env.clear_doc(docname)
 
         # read all new and changed files
         docnames = sorted(added | changed)
         # allow changing and reordering the list of docs to read
-        self.app.emit('env-before-read-docs', self.env, docnames)
+        self.events.emit('env-before-read-docs', self.env, docnames)
 
         # check if we should do parallel or serial read
         if parallel_available and len(docnames) > 5 and self.app.parallel > 1:
@@ -439,7 +441,7 @@ class Builder:
             raise SphinxError('master file %s not found' %
                               self.env.doc2path(self.config.master_doc))
 
-        for retval in self.app.emit('env-updated', self.env):
+        for retval in self.events.emit('env-updated', self.env):
             if retval is not None:
                 docnames.extend(retval)
 
@@ -453,7 +455,7 @@ class Builder:
         for docname in status_iterator(docnames, __('reading sources... '), "purple",
                                        len(docnames), self.app.verbosity):
             # remove all inventory entries for that file
-            self.app.emit('env-purge-doc', self.env, docname)
+            self.events.emit('env-purge-doc', self.env, docname)
             self.env.clear_doc(docname)
             self.read_doc(docname)
 
@@ -461,7 +463,7 @@ class Builder:
         # type: (List[str], int) -> None
         # clear all outdated docs at once
         for docname in docnames:
-            self.app.emit('env-purge-doc', self.env, docname)
+            self.events.emit('env-purge-doc', self.env, docname)
             self.env.clear_doc(docname)
 
         def read_process(docs):
diff --git a/sphinx/builders/html.py b/sphinx/builders/html.py
index 97774c668..81c64d445 100644
--- a/sphinx/builders/html.py
+++ b/sphinx/builders/html.py
@@ -653,7 +653,7 @@ class StandaloneHTMLBuilder(Builder):
     def gen_additional_pages(self):
         # type: () -> None
         # pages from extensions
-        for pagelist in self.app.emit('html-collect-pages'):
+        for pagelist in self.events.emit('html-collect-pages'):
             for pagename, context, template in pagelist:
                 self.handle_page(pagename, context, template)
 
diff --git a/sphinx/environment/__init__.py b/sphinx/environment/__init__.py
index f931b3b13..a5adcbb74 100644
--- a/sphinx/environment/__init__.py
+++ b/sphinx/environment/__init__.py
@@ -34,6 +34,7 @@ if False:
     from sphinx.application import Sphinx  # NOQA
     from sphinx.builders import Builder  # NOQA
     from sphinx.config import Config  # NOQA
+    from sphinx.event import EventManager  # NOQA
     from sphinx.domains import Domain  # NOQA
     from sphinx.project import Project  # NOQA
 
@@ -95,6 +96,7 @@ class BuildEnvironment:
         self.srcdir = None          # type: str
         self.config = None          # type: Config
         self.config_status = None   # type: int
+        self.events = None          # type: EventManager
         self.project = None         # type: Project
         self.version = None         # type: Dict[str, str]
 
@@ -190,7 +192,7 @@ class BuildEnvironment:
         # type: () -> Dict
         """Obtains serializable data for pickling."""
         __dict__ = self.__dict__.copy()
-        __dict__.update(app=None, domains={})  # clear unpickable attributes
+        __dict__.update(app=None, domains={}, events=None)  # clear unpickable attributes
         return __dict__
 
     def __setstate__(self, state):
@@ -210,6 +212,7 @@ class BuildEnvironment:
 
         self.app = app
         self.doctreedir = app.doctreedir
+        self.events = app.events
         self.srcdir = app.srcdir
         self.project = app.project
         self.version = app.registry.get_envversion(app)
@@ -307,7 +310,7 @@ class BuildEnvironment:
 
         for domainname, domain in self.domains.items():
             domain.merge_domaindata(docnames, other.domaindata[domainname])
-        app.emit('env-merge-info', self, docnames, other)
+        self.events.emit('env-merge-info', self, docnames, other)
 
     def path2doc(self, filename):
         # type: (str) -> Optional[str]
@@ -449,7 +452,7 @@ class BuildEnvironment:
     def check_dependents(self, app, already):
         # type: (Sphinx, Set[str]) -> Iterator[str]
         to_rewrite = []  # type: List[str]
-        for docnames in app.emit('env-get-updated', self):
+        for docnames in self.events.emit('env-get-updated', self):
             to_rewrite.extend(docnames)
         for docname in set(to_rewrite):
             if docname not in already:
@@ -597,7 +600,7 @@ class BuildEnvironment:
             self.temp_data = backup
 
         # allow custom references to be resolved
-        self.app.emit('doctree-resolved', doctree, docname)
+        self.events.emit('doctree-resolved', doctree, docname)
 
     def collect_relations(self):
         # type: () -> Dict[str, List[str]]
@@ -653,4 +656,4 @@ class BuildEnvironment:
         # call check-consistency for all extensions
         for domain in self.domains.values():
             domain.check_consistency()
-        self.app.emit('env-check-consistency', self)
+        self.events.emit('env-check-consistency', self)
diff --git a/sphinx/events.py b/sphinx/events.py
index 25a378d7c..df72f8f21 100644
--- a/sphinx/events.py
+++ b/sphinx/events.py
@@ -10,14 +10,20 @@
     :license: BSD, see LICENSE for details.
 """
 
+import warnings
 from collections import OrderedDict, defaultdict
 
+from sphinx.deprecation import RemovedInSphinx40Warning
 from sphinx.errors import ExtensionError
 from sphinx.locale import __
+from sphinx.util import logging
 
 if False:
     # For type annotation
     from typing import Any, Callable, Dict, List  # NOQA
+    from sphinx.application import Sphinx  # NOQA
+
+logger = logging.getLogger(__name__)
 
 
 # List of all known core events. Maps name to arguments description.
@@ -42,20 +48,28 @@ core_events = {
 
 
 class EventManager:
-    def __init__(self):
-        # type: () -> None
+    """Event manager for Sphinx."""
+
+    def __init__(self, app=None):
+        # type: (Sphinx) -> None
+        if app is None:
+            warnings.warn('app argument is required for EventManager.',
+                          RemovedInSphinx40Warning)
+        self.app = app
         self.events = core_events.copy()
         self.listeners = defaultdict(OrderedDict)  # type: Dict[str, Dict[int, Callable]]
         self.next_listener_id = 0
 
     def add(self, name):
         # type: (str) -> None
+        """Register a custom Sphinx event."""
         if name in self.events:
             raise ExtensionError(__('Event %r already present') % name)
         self.events[name] = ''
 
     def connect(self, name, callback):
         # type: (str, Callable) -> int
+        """Connect a handler to specific event."""
         if name not in self.events:
             raise ExtensionError(__('Unknown event name: %s') % name)
 
@@ -66,18 +80,35 @@ class EventManager:
 
     def disconnect(self, listener_id):
         # type: (int) -> None
+        """Disconnect a handler."""
         for event in self.listeners.values():
             event.pop(listener_id, None)
 
     def emit(self, name, *args):
         # type: (str, Any) -> List
+        """Emit a Sphinx event."""
+        try:
+            logger.debug('[app] emitting event: %r%s', name, repr(args)[:100])
+        except Exception:
+            # not every object likes to be repr()'d (think
+            # random stuff coming via autodoc)
+            pass
+
         results = []
         for callback in self.listeners[name].values():
-            results.append(callback(*args))
+            if self.app is None:
+                # for compatibility; RemovedInSphinx40Warning
+                results.append(callback(*args))
+            else:
+                results.append(callback(self.app, *args))
         return results
 
     def emit_firstresult(self, name, *args):
         # type: (str, Any) -> Any
+        """Emit a Sphinx event and returns first result.
+
+        This returns the result of the first handler that doesn't return ``None``.
+        """
         for result in self.emit(name, *args):
             if result is not None:
                 return result
diff --git a/sphinx/ext/autodoc/__init__.py b/sphinx/ext/autodoc/__init__.py
index b3fb52538..aa2f2276f 100644
--- a/sphinx/ext/autodoc/__init__.py
+++ b/sphinx/ext/autodoc/__init__.py
@@ -403,9 +403,9 @@ class Documenter:
 
         retann = self.retann
 
-        result = self.env.app.emit_firstresult(
-            'autodoc-process-signature', self.objtype, self.fullname,
-            self.object, self.options, args, retann)
+        result = self.env.events.emit_firstresult('autodoc-process-signature',
+                                                  self.objtype, self.fullname,
+                                                  self.object, self.options, args, retann)
         if result:
             args, retann = result
 
diff --git a/sphinx/ext/todo.py b/sphinx/ext/todo.py
index 1922bb49c..f43520036 100644
--- a/sphinx/ext/todo.py
+++ b/sphinx/ext/todo.py
@@ -86,7 +86,7 @@ def process_todos(app, doctree):
     if not hasattr(env, 'todo_all_todos'):
         env.todo_all_todos = []  # type: ignore
     for node in doctree.traverse(todo_node):
-        app.emit('todo-defined', node)
+        app.events.emit('todo-defined', node)
 
         newnode = node.deepcopy()
         newnode['ids'] = []