diff --git a/CHANGES b/CHANGES
index 77cd6705d46..e33bf3d5467 100644
--- a/CHANGES
+++ b/CHANGES
@@ -28,6 +28,7 @@ Features added
   directory on build man page
 * #8289: epub: Allow to suppress "duplicated ToC entry found" warnings from epub
   builder using :confval:`suppress_warnings`.
+* #8298: sphinx-quickstart: Add :option:`sphinx-quickstart --no-sep` option
 
 Bugs fixed
 ----------
diff --git a/doc/man/sphinx-quickstart.rst b/doc/man/sphinx-quickstart.rst
index 2407e3be7f4..520a420ce7f 100644
--- a/doc/man/sphinx-quickstart.rst
+++ b/doc/man/sphinx-quickstart.rst
@@ -33,6 +33,10 @@ Options
 
    If specified, separate source and build directories.
 
+.. option:: --no-sep
+
+   If specified, create build directroy under source directroy.
+
 .. option:: --dot=DOT
 
    Inside the root directory, two more directories will be created;
diff --git a/sphinx/cmd/quickstart.py b/sphinx/cmd/quickstart.py
index cad3c65e51c..2363f9fe430 100644
--- a/sphinx/cmd/quickstart.py
+++ b/sphinx/cmd/quickstart.py
@@ -489,8 +489,10 @@ def get_parser() -> argparse.ArgumentParser:
                         help=__('project root'))
 
     group = parser.add_argument_group(__('Structure options'))
-    group.add_argument('--sep', action='store_true', default=None,
+    group.add_argument('--sep', action='store_true', dest='sep', default=None,
                        help=__('if specified, separate source and build dirs'))
+    group.add_argument('--no-sep', action='store_false', dest='sep',
+                       help=__('if specified, create build dir under source dir'))
     group.add_argument('--dot', metavar='DOT', default='_',
                        help=__('replacement for dot in _templates etc.'))