diff --git a/mod/forum/db/services.php b/mod/forum/db/services.php
index f6cee741609..9f72919b3e8 100644
--- a/mod/forum/db/services.php
+++ b/mod/forum/db/services.php
@@ -183,4 +183,12 @@ $functions = array(
         'type' => 'write',
         'services' => array(MOODLE_OFFICIAL_MOBILE_SERVICE),
     ),
+    'mod_forum_get_discussion_post' => array(
+        'classname' => 'mod_forum_external',
+        'methodname' => 'get_discussion_post',
+        'classpath' => 'mod/forum/externallib.php',
+        'description' => 'Get a particular discussion post.',
+        'type' => 'read',
+        'services' => array(MOODLE_OFFICIAL_MOBILE_SERVICE)
+    ),
 );
diff --git a/mod/forum/externallib.php b/mod/forum/externallib.php
index 624e7233cde..8cca27d7063 100644
--- a/mod/forum/externallib.php
+++ b/mod/forum/externallib.php
@@ -2152,4 +2152,84 @@ class mod_forum_external extends external_api {
             )
         );
     }
+
+    /**
+     * Returns description of method parameters
+     *
+     * @return external_function_parameters
+     * @since Moodle 3.8
+     */
+    public static function get_discussion_post_parameters() {
+        return new external_function_parameters(
+            array(
+                'postid' => new external_value(PARAM_INT, 'Post to fetch.'),
+            )
+        );
+    }
+    /**
+     * Get a particular discussion post.
+     *
+     * @param int $postid post to fetch
+     * @return array of post and warnings (if any)
+     * @since Moodle 3.8
+     * @throws moodle_exception
+     */
+    public static function get_discussion_post($postid) {
+        global $USER, $CFG;
+
+        $params = self::validate_parameters(self::get_discussion_post_parameters(),
+                                            array(
+                                                'postid' => $postid,
+                                            ));
+        $warnings = array();
+        $vaultfactory = mod_forum\local\container::get_vault_factory();
+        $forumvault = $vaultfactory->get_forum_vault();
+        $discussionvault = $vaultfactory->get_discussion_vault();
+        $postvault = $vaultfactory->get_post_vault();
+
+        $postentity = $postvault->get_from_id($params['postid']);
+        if (empty($postentity)) {
+            throw new moodle_exception('invalidpostid', 'forum');
+        }
+        $discussionentity = $discussionvault->get_from_id($postentity->get_discussion_id());
+        if (empty($discussionentity)) {
+            throw new moodle_exception('notpartofdiscussion', 'forum');
+        }
+        $forumentity = $forumvault->get_from_id($discussionentity->get_forum_id());
+        if (empty($forumentity)) {
+            throw new moodle_exception('invalidforumid', 'forum');
+        }
+        self::validate_context($forumentity->get_context());
+
+        $managerfactory = mod_forum\local\container::get_manager_factory();
+        $capabilitymanager = $managerfactory->get_capability_manager($forumentity);
+
+        if (!$capabilitymanager->can_view_post($USER, $discussionentity, $postentity)) {
+            throw new moodle_exception('noviewdiscussionspermission', 'forum');
+        }
+
+        $builderfactory = mod_forum\local\container::get_builder_factory();
+        $postbuilder = $builderfactory->get_exported_posts_builder();
+        $posts = $postbuilder->build($USER, [$forumentity], [$discussionentity], [$postentity]);
+        $post = empty($posts) ? array() : reset($posts);
+
+        $result = array();
+        $result['post'] = $post;
+        $result['warnings'] = $warnings;
+        return $result;
+    }
+    /**
+     * Returns description of method result value
+     *
+     * @return external_description
+     * @since Moodle 3.8
+     */
+    public static function get_discussion_post_returns() {
+        return new external_single_structure(
+            array(
+                'post' => \mod_forum\local\exporters\post::get_read_structure(),
+                'warnings' => new external_warnings(),
+            )
+        );
+    }
 }
diff --git a/mod/forum/tests/externallib_test.php b/mod/forum/tests/externallib_test.php
index 7ee327574a1..f6e81fb5a5c 100644
--- a/mod/forum/tests/externallib_test.php
+++ b/mod/forum/tests/externallib_test.php
@@ -2604,4 +2604,103 @@ class mod_forum_external_testcase extends externallib_advanced_testcase {
         $this->expectExceptionMessage(get_string('cannotdeletepost', 'forum'));
         mod_forum_external::delete_post($post->id);
     }
+
+    /**
+     * Test get_discussion_post a discussion.
+     */
+    public function test_get_discussion_post_discussion() {
+        global $DB;
+        $this->resetAfterTest(true);
+        // Setup test data.
+        $course = $this->getDataGenerator()->create_course();
+        $forum = $this->getDataGenerator()->create_module('forum', array('course' => $course->id));
+        $user = $this->getDataGenerator()->create_user();
+        $role = $DB->get_record('role', array('shortname' => 'student'), '*', MUST_EXIST);
+        self::getDataGenerator()->enrol_user($user->id, $course->id, $role->id);
+        // Add a discussion.
+        $record = new stdClass();
+        $record->course = $course->id;
+        $record->userid = $user->id;
+        $record->forum = $forum->id;
+        $discussion = $this->getDataGenerator()->get_plugin_generator('mod_forum')->create_discussion($record);
+        $this->setUser($user);
+        $result = mod_forum_external::get_discussion_post($discussion->firstpost);
+        $result = external_api::clean_returnvalue(mod_forum_external::get_discussion_post_returns(), $result);
+        $this->assertEquals($discussion->firstpost, $result['post']['id']);
+        $this->assertFalse($result['post']['hasparent']);
+        $this->assertEquals($discussion->message, $result['post']['message']);
+    }
+
+    /**
+     * Test get_discussion_post a post.
+     */
+    public function test_get_discussion_post_post() {
+        global $DB;
+        $this->resetAfterTest(true);
+        // Setup test data.
+        $course = $this->getDataGenerator()->create_course();
+        $forum = $this->getDataGenerator()->create_module('forum', array('course' => $course->id));
+        $user = $this->getDataGenerator()->create_user();
+        $role = $DB->get_record('role', array('shortname' => 'student'), '*', MUST_EXIST);
+        self::getDataGenerator()->enrol_user($user->id, $course->id, $role->id);
+        // Add a discussion.
+        $record = new stdClass();
+        $record->course = $course->id;
+        $record->userid = $user->id;
+        $record->forum = $forum->id;
+        $discussion = $this->getDataGenerator()->get_plugin_generator('mod_forum')->create_discussion($record);
+        $parentpost = $DB->get_record('forum_posts', array('discussion' => $discussion->id));
+        // Add a post.
+        $record = new stdClass();
+        $record->course = $course->id;
+        $record->userid = $user->id;
+        $record->forum = $forum->id;
+        $record->discussion = $discussion->id;
+        $record->parent = $parentpost->id;
+        $post = $this->getDataGenerator()->get_plugin_generator('mod_forum')->create_post($record);
+        $this->setUser($user);
+        $result = mod_forum_external::get_discussion_post($post->id);
+        $result = external_api::clean_returnvalue(mod_forum_external::get_discussion_post_returns(), $result);
+        $this->assertEquals($post->id, $result['post']['id']);
+        $this->assertTrue($result['post']['hasparent']);
+        $this->assertEquals($post->message, $result['post']['message']);
+    }
+
+    /**
+     * Test get_discussion_post a different user post.
+     */
+    public function test_get_discussion_post_other_user_post() {
+        global $DB;
+        $this->resetAfterTest(true);
+        // Setup test data.
+        $course = $this->getDataGenerator()->create_course();
+        $forum = $this->getDataGenerator()->create_module('forum', array('course' => $course->id));
+        $user = $this->getDataGenerator()->create_user();
+        $otheruser = $this->getDataGenerator()->create_user();
+        $role = $DB->get_record('role', array('shortname' => 'student'), '*', MUST_EXIST);
+        self::getDataGenerator()->enrol_user($user->id, $course->id, $role->id);
+        self::getDataGenerator()->enrol_user($otheruser->id, $course->id, $role->id);
+        // Add a discussion.
+        $record = array();
+        $record['course'] = $course->id;
+        $record['forum'] = $forum->id;
+        $record['userid'] = $user->id;
+        $discussion = $this->getDataGenerator()->get_plugin_generator('mod_forum')->create_discussion($record);
+        $parentpost = $DB->get_record('forum_posts', array('discussion' => $discussion->id));
+        // Add a post.
+        $record = new stdClass();
+        $record->course = $course->id;
+        $record->userid = $user->id;
+        $record->forum = $forum->id;
+        $record->discussion = $discussion->id;
+        $record->parent = $parentpost->id;
+        $post = $this->getDataGenerator()->get_plugin_generator('mod_forum')->create_post($record);
+        // Check other user post.
+        $this->setUser($otheruser);
+        $result = mod_forum_external::get_discussion_post($post->id);
+        $result = external_api::clean_returnvalue(mod_forum_external::get_discussion_post_returns(), $result);
+        $this->assertEquals($post->id, $result['post']['id']);
+        $this->assertTrue($result['post']['hasparent']);
+        $this->assertEquals($post->message, $result['post']['message']);
+    }
 }