diff --git a/CHANGES b/CHANGES
index ef0bf0440..e33793525 100644
--- a/CHANGES
+++ b/CHANGES
@@ -40,6 +40,7 @@ Bugs fixed
 * autodoc: ImportError is replaced by AttributeError for deeper module
 * #2720, #4034: Incorrect links with ``:download:``, duplicate names, and
   parallel builds
+* #5290: autodoc: failed to analyze source code in egg package
 
 Testing
 --------
diff --git a/sphinx/pycode/__init__.py b/sphinx/pycode/__init__.py
index c4c055bf5..a97903a27 100644
--- a/sphinx/pycode/__init__.py
+++ b/sphinx/pycode/__init__.py
@@ -10,6 +10,9 @@
 """
 from __future__ import print_function
 
+import re
+from zipfile import ZipFile
+
 from six import iteritems, BytesIO, StringIO
 
 from sphinx.errors import PycodeError
@@ -42,9 +45,23 @@ class ModuleAnalyzer(object):
                 obj = cls(f, modname, filename)  # type: ignore
                 cls.cache['file', filename] = obj
         except Exception as err:
-            raise PycodeError('error opening %r' % filename, err)
+            if '.egg/' in filename:
+                obj = cls.cache['file', filename] = cls.for_egg(filename, modname)
+            else:
+                raise PycodeError('error opening %r' % filename, err)
         return obj
 
+    @classmethod
+    def for_egg(cls, filename, modname):
+        # type: (unicode, unicode) -> ModuleAnalyzer
+        eggpath, relpath = re.split('(?<=\\.egg)/', filename)
+        try:
+            with ZipFile(eggpath) as egg:
+                code = egg.read(relpath).decode('utf-8')
+                return cls.for_string(code, modname, filename)
+        except Exception as exc:
+            raise PycodeError('error opening %r' % filename, exc)
+
     @classmethod
     def for_module(cls, modname):
         # type: (str) -> ModuleAnalyzer
diff --git a/sphinx/util/__init__.py b/sphinx/util/__init__.py
index 29038978a..0c0c22c9c 100644
--- a/sphinx/util/__init__.py
+++ b/sphinx/util/__init__.py
@@ -314,6 +314,11 @@ def get_module_source(modname):
             filename += 'w'
     elif not (lfilename.endswith('.py') or lfilename.endswith('.pyw')):
         raise PycodeError('source is not a .py file: %r' % filename)
+    elif '.egg' in filename:
+        eggpath, _ = re.split('(?<=\\.egg)/', filename)
+        if path.isfile(eggpath):
+            return 'file', filename
+
     if not path.isfile(filename):
         raise PycodeError('source file is not present: %r' % filename)
     return 'file', filename
diff --git a/tests/roots/test-pycode-egg/conf.py b/tests/roots/test-pycode-egg/conf.py
new file mode 100644
index 000000000..a8e25882b
--- /dev/null
+++ b/tests/roots/test-pycode-egg/conf.py
@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+
+import os
+import sys
+
+sys.path.insert(0, os.path.abspath('sample-0.0.0-py3.7.egg'))
+master_doc = 'index'
+extensions = ['sphinx.ext.autodoc']
diff --git a/tests/roots/test-pycode-egg/index.rst b/tests/roots/test-pycode-egg/index.rst
new file mode 100644
index 000000000..affc7912a
--- /dev/null
+++ b/tests/roots/test-pycode-egg/index.rst
@@ -0,0 +1,2 @@
+test-pycode-egg
+===============
diff --git a/tests/roots/test-pycode-egg/sample-0.0.0-py3.7.egg b/tests/roots/test-pycode-egg/sample-0.0.0-py3.7.egg
new file mode 100644
index 000000000..719dbea51
Binary files /dev/null and b/tests/roots/test-pycode-egg/sample-0.0.0-py3.7.egg differ
diff --git a/tests/roots/test-pycode-egg/src/sample.py b/tests/roots/test-pycode-egg/src/sample.py
new file mode 100644
index 000000000..c4d3d61e8
--- /dev/null
+++ b/tests/roots/test-pycode-egg/src/sample.py
@@ -0,0 +1,8 @@
+# -*- coding: utf-8 -*-
+
+#: constant on sample.py
+CONSTANT = 1
+
+
+def hello(s):
+    print('Hello %s' % s)
diff --git a/tests/roots/test-pycode-egg/src/setup.py b/tests/roots/test-pycode-egg/src/setup.py
new file mode 100644
index 000000000..f23c80a06
--- /dev/null
+++ b/tests/roots/test-pycode-egg/src/setup.py
@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+from setuptools import setup
+
+
+setup(name='sample',
+      py_modules=['sample'])
diff --git a/tests/test_autodoc.py b/tests/test_autodoc.py
index cefceb833..e2dc37c56 100644
--- a/tests/test_autodoc.py
+++ b/tests/test_autodoc.py
@@ -1584,3 +1584,26 @@ def test_autodoc_default_options_with_values(app):
         assert '      list of weak references to the object (if defined)' not in actual
     assert '   .. py:method:: CustomIter.snafucate()' not in actual
     assert '      Makes this snafucated.' not in actual
+
+
+@pytest.mark.sphinx('html', testroot='pycode-egg')
+def test_autodoc_for_egged_code(app):
+    options = {"members": None,
+               "undoc-members": None}
+    actual = do_autodoc(app, 'module', 'sample', options)
+    assert list(actual) == [
+        '',
+        '.. py:module:: sample',
+        '',
+        '',
+        '.. py:data:: CONSTANT',
+        '   :module: sample',
+        '   :annotation: = 1',
+        '',
+        '   constant on sample.py',
+        '   ',
+        '',
+        '.. py:function:: hello(s)',
+        '   :module: sample',
+        ''
+    ]
diff --git a/tests/test_pycode.py b/tests/test_pycode.py
index b4385e8a6..2eab456bc 100644
--- a/tests/test_pycode.py
+++ b/tests/test_pycode.py
@@ -10,6 +10,7 @@
 """
 
 import os
+import sys
 
 from six import PY2
 
@@ -47,6 +48,31 @@ def test_ModuleAnalyzer_for_module():
     assert analyzer.encoding == 'utf-8'
 
 
+def test_ModuleAnalyzer_for_file_in_egg(rootdir):
+    try:
+        path = rootdir / 'test-pycode-egg' / 'sample-0.0.0-py3.7.egg'
+        sys.path.insert(0, path)
+
+        import sample
+        analyzer = ModuleAnalyzer.for_file(sample.__file__, 'sample')
+        docs = analyzer.find_attr_docs()
+        assert docs == {('', 'CONSTANT'): ['constant on sample.py', '']}
+    finally:
+        sys.path.pop(0)
+
+
+def test_ModuleAnalyzer_for_module_in_egg(rootdir):
+    try:
+        path = rootdir / 'test-pycode-egg' / 'sample-0.0.0-py3.7.egg'
+        sys.path.insert(0, path)
+
+        analyzer = ModuleAnalyzer.for_module('sample')
+        docs = analyzer.find_attr_docs()
+        assert docs == {('', 'CONSTANT'): ['constant on sample.py', '']}
+    finally:
+        sys.path.pop(0)
+
+
 def test_ModuleAnalyzer_find_tags():
     code = ('class Foo(object):\n'  # line: 1
             '    """class Foo!"""\n'