diff --git a/source/blender/editors/space_outliner/CMakeLists.txt b/source/blender/editors/space_outliner/CMakeLists.txt
index 1c09ad2d98f..97d2957eed2 100644
--- a/source/blender/editors/space_outliner/CMakeLists.txt
+++ b/source/blender/editors/space_outliner/CMakeLists.txt
@@ -58,6 +58,7 @@ set(SRC
   tree/tree_element_scene_objects.cc
   tree/tree_element_seq.cc
   tree/tree_element_view_layer.cc
+  tree/tree_iterator.cc
 
   outliner_intern.hh
   tree/common.hh
@@ -76,6 +77,7 @@ set(SRC
   tree/tree_element_scene_objects.hh
   tree/tree_element_seq.hh
   tree/tree_element_view_layer.hh
+  tree/tree_iterator.hh
 )
 
 set(LIB
diff --git a/source/blender/editors/space_outliner/tree/tree_iterator.cc b/source/blender/editors/space_outliner/tree/tree_iterator.cc
new file mode 100644
index 00000000000..85ff9e6437e
--- /dev/null
+++ b/source/blender/editors/space_outliner/tree/tree_iterator.cc
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup spoutliner
+ */
+
+#include "DNA_space_types.h"
+
+#include "BLI_listbase.h"
+
+#include "../outliner_intern.hh"
+
+#include "tree_iterator.hh"
+
+namespace blender::ed::outliner::tree_iterator {
+
+void all(const SpaceOutliner &space_outliner, const VisitorFn visitor)
+{
+  all_open(space_outliner, space_outliner.tree, visitor);
+}
+
+void all(const ListBase &subtree, const VisitorFn visitor)
+{
+  LISTBASE_FOREACH_MUTABLE (TreeElement *, element, &subtree) {
+    /* Get needed data out in case element gets freed. */
+    const ListBase subtree = element->subtree;
+
+    visitor(element);
+    /* Don't access element from now on, it may be freed. */
+
+    all(subtree, visitor);
+  }
+}
+
+void all_open(const SpaceOutliner &space_outliner, const VisitorFn visitor)
+{
+  all_open(space_outliner, space_outliner.tree, visitor);
+}
+
+void all_open(const SpaceOutliner &space_outliner,
+              const ListBase &subtree,
+              const VisitorFn visitor)
+{
+  LISTBASE_FOREACH_MUTABLE (TreeElement *, element, &subtree) {
+    /* Get needed data out in case element gets freed. */
+    const bool is_open = TSELEM_OPEN(element->store_elem, &space_outliner);
+    const ListBase subtree = element->subtree;
+
+    visitor(element);
+    /* Don't access element from now on, it may be freed. */
+
+    if (is_open) {
+      all_open(space_outliner, subtree, visitor);
+    }
+  }
+}
+
+}  // namespace blender::ed::outliner::tree_iterator
diff --git a/source/blender/editors/space_outliner/tree/tree_iterator.hh b/source/blender/editors/space_outliner/tree/tree_iterator.hh
new file mode 100644
index 00000000000..e3b3c90eaad
--- /dev/null
+++ b/source/blender/editors/space_outliner/tree/tree_iterator.hh
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/** \file
+ * \ingroup spoutliner
+ */
+
+#pragma once
+
+#include "BLI_function_ref.hh"
+
+struct ListBase;
+struct SpaceOutliner;
+struct TreeElement;
+
+namespace blender::ed::outliner {
+namespace tree_iterator {
+
+using VisitorFn = FunctionRef<void(TreeElement *)>;
+
+/**
+ * Preorder (meaning depth-first) traversal of all elements (regardless of collapsed state).
+ * Freeing the currently visited element in \a visitor is fine.
+ */
+void all(const SpaceOutliner &space_outliner, VisitorFn visitor);
+void all(const ListBase &subtree, VisitorFn visitor);
+
+/**
+ * Preorder (meaning depth-first) traversal of all elements not part of a collapsed sub-tree.
+ * Freeing the currently visited element in \a visitor is fine.
+ */
+void all_open(const SpaceOutliner &, VisitorFn visitor);
+void all_open(const SpaceOutliner &, const ListBase &subtree, VisitorFn visitor);
+
+}  // namespace tree_iterator
+}  // namespace blender::ed::outliner