diff --git a/CHANGES.rst b/CHANGES.rst
index a02119c1e..8632ec5ad 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -147,6 +147,9 @@ Bugs fixed
 * #12040: HTML Search: Ensure that document titles that are partially-matched by
   the user search query are included in search results.
   Patch by James Addison.
+* #11970: singlehtml builder: make target URIs to be same-document references in
+  the sense of :rfc:`RFC 3986, §4.4 <3986#section-4.4>`, e.g., ``index.html#foo``
+  becomes ``#foo``. Patch by eanorige.
 
 Testing
 -------
diff --git a/sphinx/builders/singlehtml.py b/sphinx/builders/singlehtml.py
index 87590544f..efc4eaa2f 100644
--- a/sphinx/builders/singlehtml.py
+++ b/sphinx/builders/singlehtml.py
@@ -41,8 +41,7 @@ class SingleFileHTMLBuilder(StandaloneHTMLBuilder):
     def get_target_uri(self, docname: str, typ: str | None = None) -> str:
         if docname in self.env.all_docs:
             # all references are on the same page...
-            return self.config.root_doc + self.out_suffix + \
-                '#document-' + docname
+            return '#document-' + docname
         else:
             # chances are this is a html_additional_page
             return docname + self.out_suffix