diff --git a/.upgradenotes/MDL-82381-2025022716072475.yml b/.upgradenotes/MDL-82381-2025022716072475.yml
new file mode 100644
index 00000000000..a410c2597b7
--- /dev/null
+++ b/.upgradenotes/MDL-82381-2025022716072475.yml
@@ -0,0 +1,5 @@
+issueNumber: MDL-82381
+notes:
+  report_progress:
+    - message: Added a new optional parameter $activegroup to render_groups_select()
+      type: changed
diff --git a/report/progress/classes/output/renderer.php b/report/progress/classes/output/renderer.php
index da58da02fc1..a287c1a0c30 100644
--- a/report/progress/classes/output/renderer.php
+++ b/report/progress/classes/output/renderer.php
@@ -77,12 +77,31 @@ class renderer extends plugin_renderer_base {
      *
      * @param \moodle_url $url The base url.
      * @param \stdClass $course Current course.
+     * @param int $activegroup Currently active group, defaults to 0. Has no effect if course is in separate groups mode.
      * @return string HTML
      */
-    public function render_groups_select(\moodle_url $url, \stdClass $course): string {
+    public function render_groups_select(\moodle_url $url, \stdClass $course, int $activegroup = 0): string {
+        global $USER;
         $groupurl = fullclone($url);
         $groupurl->remove_params(['page', 'group']);
-        $groupoutput = groups_print_course_menu($course, $groupurl, true);
+        $groupoutput = '';
+        if ($course->groupmode == SEPARATEGROUPS) {
+            $groupoutput = groups_print_course_menu($course, $groupurl, true);
+        } else {
+            if (has_capability('moodle/site:accessallgroups', \context_course::instance($course->id))) {
+                $groups = groups_get_all_groups($course->id);
+            } else {
+                $groups = groups_get_all_groups($course->id, $USER->id);
+            }
+
+            if (count($groups) == 0) {
+                return '';
+            }
+            $groupsmenu = [get_string('allparticipants')] + groups_list_to_menu($groups);
+            $select = new single_select($groupurl, 'group', $groupsmenu, $activegroup, null, 'selectgroup');
+            $select->label = get_string('groups');
+            $groupoutput = $this->output->render($select);
+        }
 
         if (empty($groupoutput)) {
             return $groupoutput;
diff --git a/report/progress/index.php b/report/progress/index.php
index 5f0437a15cb..a92f8d1a401 100644
--- a/report/progress/index.php
+++ b/report/progress/index.php
@@ -108,7 +108,16 @@ require_login($course);
 require_capability('report/progress:view',$context);
 
 // Get group mode
-$group = groups_get_course_group($course,true); // Supposed to verify group
+if ($course->groupmode == SEPARATEGROUPS) {
+    $group = groups_get_course_group($course, true); // Supposed to verify group.
+} else {
+    if (groups_group_visible($groupid, $course)) {
+        $group = $groupid;
+    } else {
+        $group = 0;
+    }
+}
+
 if ($group===0 && $course->groupmode==SEPARATEGROUPS) {
     require_capability('moodle/site:accessallgroups',$context);
 }
@@ -205,7 +214,7 @@ if ($csv && $grandtotal && count($activities)>0) { // Only show CSV if there are
     $PAGE->requires->js_call_amd('report_progress/completion_override', 'init', [fullname($USER)]);
 
     // Handle groups (if enabled).
-    echo $output->render_groups_select($url, $course);
+    echo $output->render_groups_select($url, $course, $group);
 
     // Display include activity filter.
     echo $output->render_include_activity_select($url, $activitytypes, $activityinclude);
diff --git a/report/progress/tests/behat/activity_completion_report_filter_group_without_groupmode.feature b/report/progress/tests/behat/activity_completion_report_filter_group_without_groupmode.feature
new file mode 100644
index 00000000000..47cd8dce899
--- /dev/null
+++ b/report/progress/tests/behat/activity_completion_report_filter_group_without_groupmode.feature
@@ -0,0 +1,62 @@
+@report @report_progress
+Feature: Teacher can view and filter activity completion data by group if group mode is not set.
+
+  Background:
+    Given the following "course" exists:
+      | fullname         | Course 1 |
+      | shortname        | C1       |
+      | format           | topics   |
+      | enablecompletion | 1        |
+      | groupmode        | 0        |
+      | initsections     | 1        |
+    And the following "activities" exist:
+      | activity | name          | intro   | course | idnumber | section | completion | completionview |
+      | quiz     | My quiz B     | A3 desc | C1     | quizb    | 0       | 2          | 1              |
+      | quiz     | My quiz A     | A3 desc | C1     | quiza    | 1       | 2          | 1              |
+      | page     | My page       | A4 desc | C1     | page1    | 2       | 2          | 1              |
+      | assign   | My assignment | A1 desc | C1     | assign1  | 2       | 2          | 1              |
+    And the following "users" exist:
+      | username | firstname | lastname | email                |
+      | teacher1 | Teacher   | One      | teacher1@example.com |
+      | student1 | Student   | One      | student1@example.com |
+      | student2 | Student   | Two      | student2@example.com |
+    And the following "groups" exist:
+      | name    | course | idnumber |
+      | Group 1 | C1     | G1       |
+      | Group 2 | C1     | G2       |
+    And the following "course enrolments" exist:
+      | user     | course | role           |
+      | teacher1 | C1     | editingteacher |
+      | student1 | C1     | student        |
+      | student2 | C1     | student        |
+    And the following "group members" exist:
+      | user     | group |
+      | student1 | G1    |
+      | student2 | G2    |
+      | teacher1 | G1    |
+      | teacher1 | G2    |
+
+  @javascript
+  Scenario: Teacher can view the activity completion report using filtering and sorting options.
+    Given I am on the "Course 1" course page logged in as "teacher1"
+    When I navigate to "Reports" in current page administration
+    And I click on "Activity completion" "link"
+    Then "My quiz B" "link" should appear before "My quiz A" "link" in the "completion-progress" "table"
+    And I set the field "Groups" to "Group 1"
+    And I set the field "Include" to "Quizzes"
+    And I set the field "Activity order" to "Alphabetical"
+    And "My quiz A" "link" should appear before "My quiz B" "link" in the "completion-progress" "table"
+    And I should not see "My assignment" in the "completion-progress" "table"
+    And I should not see "My page" in the "completion-progress" "table"
+    And I should see "Student One" in the "completion-progress" "table"
+    And I should not see "Student Two" in the "completion-progress" "table"
+    And I set the field "Groups" to "All participants"
+    And I set the field "Include" to "All activities and resources"
+    And I set the field "Section" to "Section 1"
+    And I should not see "My assignment" in the "completion-progress" "table"
+    And I should not see "My page" in the "completion-progress" "table"
+    And I should not see "My assignment" in the "completion-progress" "table"
+    And I should not see "My quiz B" in the "completion-progress" "table"
+    And I should see "My quiz A" in the "completion-progress" "table"
+    And I should see "Quiz" in the "activityinclude" "select"
+    And I should not see "Page" in the "activityinclude" "select"