diff --git a/blocks/classes/local/views/secondary.php b/blocks/classes/navigation/views/secondary.php
similarity index 96%
rename from blocks/classes/local/views/secondary.php
rename to blocks/classes/navigation/views/secondary.php
index c23e857a5f7..43acdadf8c8 100644
--- a/blocks/classes/local/views/secondary.php
+++ b/blocks/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace core_block\local\views;
+namespace core_block\navigation\views;
 
 /**
  * Class secondary
diff --git a/lib/blocklib.php b/lib/blocklib.php
index 9c4f2badbfc..f6fc929087d 100644
--- a/lib/blocklib.php
+++ b/lib/blocklib.php
@@ -1684,12 +1684,20 @@ class block_manager {
      * Convenience function to check whether a block is implementing a secondary nav class and return it
      * initialised to the calling function
      *
+     * @todo MDL-74939 Remove support for old 'local\views\secondary' class location
      * @param block_base $block
      * @return \core\navigation\views\secondary
      */
     protected function get_secondarynav(block_base $block): \core\navigation\views\secondary {
-        $class = "core_block\\local\\views\\secondary";
-        if (class_exists("block_{$block->name()}\\local\\views\\secondary")) {
+        $class = "core_block\\navigation\\views\\secondary";
+        if (class_exists("block_{$block->name()}\\navigation\\views\\secondary")) {
+            $class = "block_{$block->name()}\\navigation\\views\\secondary";
+        } else if (class_exists("block_{$block->name()}\\local\\views\\secondary")) {
+            // For backwards compatibility, support the old location for this class (it was in a
+            // 'local' namespace which shouldn't be used for core APIs).
+            debugging("The class block_{$block->name()}\\local\\views\\secondary uses a deprecated " .
+                    "namespace. Please move it to block_{$block->name()}\\navigation\\views\\secondary.",
+                    DEBUG_DEVELOPER);
             $class = "block_{$block->name()}\\local\\views\\secondary";
         }
         $secondarynav = new $class($this->page);
diff --git a/lib/pagelib.php b/lib/pagelib.php
index 26cc6e5f86d..04bba10aff9 100644
--- a/lib/pagelib.php
+++ b/lib/pagelib.php
@@ -867,13 +867,22 @@ class moodle_page {
 
     /**
      * Returns the secondary navigation object
+     *
+     * @todo MDL-74939 Remove support for old 'local\views\secondary' class location
      * @return secondary
      */
     protected function magic_get_secondarynav() {
         if ($this->_secondarynav === null) {
             $class = 'core\navigation\views\secondary';
             // Try and load a custom class first.
-            if (class_exists("mod_{$this->activityname}\\local\\views\\secondary")) {
+            if (class_exists("mod_{$this->activityname}\\navigation\\views\\secondary")) {
+                $class = "mod_{$this->activityname}\\navigation\\views\\secondary";
+            } else if (class_exists("mod_{$this->activityname}\\local\\views\\secondary")) {
+                // For backwards compatibility, support the old location for this class (it was in a
+                // 'local' namespace which shouldn't be used for core APIs).
+                debugging("The class mod_{$this->activityname}}\\local\\views\\secondary uses a deprecated " .
+                        "namespace. Please move it to mod_{$this->activityname}\\navigation\\views\\secondary.",
+                        DEBUG_DEVELOPER);
                 $class = "mod_{$this->activityname}\\local\\views\\secondary";
             }
 
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index 89285a3313c..903b32b332b 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -12,6 +12,9 @@ information provided here is intended especially for developers.
   an event exists with the given criteria (see MDL-72723 for details).
    - Breaking: 3rd party log readers implementing interface sql_reader will need to implement get_events_select_exists()
 * Added $strictness parameter to persistent `get_record` method, optionally allowing caller to ensure record exists
+* For plugins that override secondary navigation, the namespace for the custom secondary navigation class has
+  changed. It was (for example) mod_mymodule\local\views\secondary but is now
+  mod_mymodule\navigation\views\secondary. The old location will continue to work, but is deprecated.
 
 === 4.0 ===
 
diff --git a/mod/assign/classes/local/views/secondary.php b/mod/assign/classes/navigation/views/secondary.php
similarity index 97%
rename from mod/assign/classes/local/views/secondary.php
rename to mod/assign/classes/navigation/views/secondary.php
index 4b490964c15..e7a83770c10 100644
--- a/mod/assign/classes/local/views/secondary.php
+++ b/mod/assign/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace mod_assign\local\views;
+namespace mod_assign\navigation\views;
 
 use core\navigation\views\secondary as core_secondary;
 
diff --git a/mod/feedback/classes/local/views/secondary.php b/mod/feedback/classes/navigation/views/secondary.php
similarity index 98%
rename from mod/feedback/classes/local/views/secondary.php
rename to mod/feedback/classes/navigation/views/secondary.php
index 2aaa9d39eeb..e61d5aef411 100644
--- a/mod/feedback/classes/local/views/secondary.php
+++ b/mod/feedback/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace mod_feedback\local\views;
+namespace mod_feedback\navigation\views;
 
 use core\navigation\views\secondary as core_secondary;
 use settings_navigation;
diff --git a/mod/glossary/classes/local/views/secondary.php b/mod/glossary/classes/navigation/views/secondary.php
similarity index 97%
rename from mod/glossary/classes/local/views/secondary.php
rename to mod/glossary/classes/navigation/views/secondary.php
index 83e2edd46e8..0c1b7fec585 100644
--- a/mod/glossary/classes/local/views/secondary.php
+++ b/mod/glossary/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace mod_glossary\local\views;
+namespace mod_glossary\navigation\views;
 
 use core\navigation\views\secondary as core_secondary;
 
diff --git a/mod/label/classes/local/views/secondary.php b/mod/label/classes/navigation/views/secondary.php
similarity index 98%
rename from mod/label/classes/local/views/secondary.php
rename to mod/label/classes/navigation/views/secondary.php
index bba9e330302..64be842fd86 100644
--- a/mod/label/classes/local/views/secondary.php
+++ b/mod/label/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace mod_label\local\views;
+namespace mod_label\navigation\views;
 
 use core\navigation\views\secondary as core_secondary;
 use settings_navigation;
diff --git a/mod/quiz/classes/local/views/secondary.php b/mod/quiz/classes/navigation/views/secondary.php
similarity index 98%
rename from mod/quiz/classes/local/views/secondary.php
rename to mod/quiz/classes/navigation/views/secondary.php
index e9be56666a4..89a6d3f17a9 100644
--- a/mod/quiz/classes/local/views/secondary.php
+++ b/mod/quiz/classes/navigation/views/secondary.php
@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 
-namespace mod_quiz\local\views;
+namespace mod_quiz\navigation\views;
 
 use core\navigation\views\secondary as core_secondary;