diff --git a/CHANGES b/CHANGES
index 583bece5c41..9409e16aa3f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -63,6 +63,7 @@ Features added
   ``no-scaled-link`` class
 * #7144: Add CSS class indicating its domain for each desc node
 * #7211: latex: Use babel for Chinese document when using XeLaTeX
+* #7220: genindex: Show "main" index entries at first
 
 Bugs fixed
 ----------
diff --git a/sphinx/environment/adapters/indexentries.py b/sphinx/environment/adapters/indexentries.py
index 1d135bd32bf..dbc94f846a8 100644
--- a/sphinx/environment/adapters/indexentries.py
+++ b/sphinx/environment/adapters/indexentries.py
@@ -7,7 +7,7 @@
     :copyright: Copyright 2007-2020 by the Sphinx team, see AUTHORS.
     :license: BSD, see LICENSE for details.
 """
-import bisect
+
 import re
 import unicodedata
 from itertools import groupby
@@ -52,8 +52,7 @@ def add_entry(word: str, subword: str, main: str, link: bool = True,
                 except NoUri:
                     pass
                 else:
-                    # maintain links in sorted/deterministic order
-                    bisect.insort(entry[0], (main, uri))
+                    entry[0].append((main, uri))
 
         domain = cast(IndexDomain, self.env.get_domain('index'))
         for fn, entries in domain.entries.items():
@@ -89,6 +88,16 @@ def add_entry(word: str, subword: str, main: str, link: bool = True,
                 except ValueError as err:
                     logger.warning(str(err), location=fn)
 
+        # sort the index entries for same keyword.
+        def keyfunc0(entry: Tuple[str, str]) -> Tuple[bool, str]:
+            main, uri = entry
+            return (not main, uri)  # show main entries at first
+
+        for indexentry in new.values():
+            indexentry[0] = sorted(indexentry[0], key=keyfunc0)
+            for subentry in indexentry[1].values():
+                subentry[0] = sorted(subentry[0], key=keyfunc0)  # type: ignore
+
         # sort the index entries; put all symbols at the front, even those
         # following the letters in ASCII, this is where the chr(127) comes from
         def keyfunc(entry: Tuple[str, List]) -> Tuple[str, str]:
diff --git a/tests/test_environment_indexentries.py b/tests/test_environment_indexentries.py
index 685b365992c..97882d44b33 100644
--- a/tests/test_environment_indexentries.py
+++ b/tests/test_environment_indexentries.py
@@ -112,6 +112,21 @@ def test_create_seealso_index(app):
     assert index[2] == ('S', [('Sphinx', [[], [('see also documentation tool', [])], None])])
 
 
+@pytest.mark.sphinx('dummy', freshenv=True)
+def test_create_main_index(app):
+    text = (".. index:: !docutils\n"
+            ".. index:: docutils\n"
+            ".. index:: pip; install\n"
+            ".. index:: !pip; install\n")
+    restructuredtext.parse(app, text)
+    index = IndexEntries(app.env).create_index(app.builder)
+    assert len(index) == 2
+    assert index[0] == ('D', [('docutils', [[('main', '#index-0'),
+                                             ('', '#index-1')], [], None])])
+    assert index[1] == ('P', [('pip', [[], [('install', [('main', '#index-3'),
+                                                         ('', '#index-2')])], None])])
+
+
 @pytest.mark.sphinx('dummy', freshenv=True)
 def test_create_index_with_name(app):
     text = (".. index:: single: docutils\n"