diff --git a/Doc/library/errno.rst b/Doc/library/errno.rst
index 1cbd51c582c..93bdb6ca9b8 100644
--- a/Doc/library/errno.rst
+++ b/Doc/library/errno.rst
@@ -637,3 +637,8 @@ defined by the module.  The specific list of defined symbols is available as
 
    Quota exceeded
 
+.. data:: EQFULL
+
+   Interface output queue is full
+
+   .. versionadded:: 3.11
diff --git a/Misc/NEWS.d/next/Library/2021-02-02-20-11-14.bpo-42971.OpVoFu.rst b/Misc/NEWS.d/next/Library/2021-02-02-20-11-14.bpo-42971.OpVoFu.rst
new file mode 100644
index 00000000000..97c8d2d79aa
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-02-02-20-11-14.bpo-42971.OpVoFu.rst
@@ -0,0 +1,2 @@
+Add definition of ``errno.EQFULL`` for platforms that define this constant
+(such as macOS).
diff --git a/Modules/errnomodule.c b/Modules/errnomodule.c
index d99bed45bd6..bf6766e0234 100644
--- a/Modules/errnomodule.c
+++ b/Modules/errnomodule.c
@@ -920,6 +920,9 @@ errno_exec(PyObject *module)
 #ifdef ESHLIBVERS
     add_errcode("ESHLIBVERS", ESHLIBVERS, "Shared library version mismatch");
 #endif
+#ifdef EQFULL
+    add_errcode("EQFULL", EQFULL, "Interface output queue is full");
+#endif
 
     Py_DECREF(error_dict);
     return 0;