diff --git a/.upgradenotes/MDL-81920-2024061811464967.yml b/.upgradenotes/MDL-81920-2024061811464967.yml
new file mode 100644
index 00000000000..c3b7b437bd9
--- /dev/null
+++ b/.upgradenotes/MDL-81920-2024061811464967.yml
@@ -0,0 +1,12 @@
+issueNumber: MDL-81920
+notes:
+  core:
+    - message: >
+        The following classes have been moved into the `\core` namespace and now
+        support autoloading:
+
+
+        - `emoticon_manager`
+
+        - `lang_string`
+      type: improved
diff --git a/lib/classes/emoticon_manager.php b/lib/classes/emoticon_manager.php
new file mode 100644
index 00000000000..44351c022bd
--- /dev/null
+++ b/lib/classes/emoticon_manager.php
@@ -0,0 +1,191 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// 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;
+
+use pix_emoticon;
+use stdClass;
+
+/**
+ * Provides core support for plugins that have to deal with emoticons (like HTML editor or emoticon filter).
+ *
+ * Whenever this manager mentiones 'emoticon object', the following data structure is expected:
+ * stdClass with properties text, imagename, imagecomponent, altidentifier and altcomponent
+ *
+ * @see \admin_setting_emoticons
+ *
+ * @package     core
+ * @copyright   2010 David Mudrak
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class emoticon_manager {
+
+    /**
+     * Returns the currently enabled emoticons
+     *
+     * @param bool $selectable If true, only return emoticons that should be selectable from a list
+     * @return stdClass[] array of emoticon objects
+     */
+    public function get_emoticons(
+        bool $selectable = false,
+    ): array {
+        global $CFG;
+
+        $notselectable = ['martin', 'egg'];
+
+        if (empty($CFG->emoticons)) {
+            return [];
+        }
+
+        $emoticons = $this->decode_stored_config($CFG->emoticons);
+
+        if (!is_array($emoticons)) {
+            // Something is wrong with the format of stored setting.
+            debugging('Invalid format of emoticons setting, please resave the emoticons settings form', DEBUG_NORMAL);
+            return [];
+        }
+
+        if ($selectable) {
+            foreach ($emoticons as $index => $emote) {
+                if (in_array($emote->altidentifier, $notselectable)) {
+                    // Skip this one.
+                    unset($emoticons[$index]);
+                }
+            }
+        }
+
+        return $emoticons;
+    }
+
+    /**
+     * Converts emoticon object into renderable pix_emoticon object
+     *
+     * @param stdClass $emoticon emoticon object
+     * @param array $attributes explicit HTML attributes to set
+     * @return pix_emoticon
+     */
+    public function prepare_renderable_emoticon(
+        stdClass $emoticon,
+        array $attributes = [],
+    ): pix_emoticon {
+        $stringmanager = get_string_manager();
+        if ($stringmanager->string_exists($emoticon->altidentifier, $emoticon->altcomponent)) {
+            $alt = get_string($emoticon->altidentifier, $emoticon->altcomponent);
+        } else {
+            $alt = s($emoticon->text);
+        }
+        return new pix_emoticon($emoticon->imagename, $alt, $emoticon->imagecomponent, $attributes);
+    }
+
+    /**
+     * Encodes the array of emoticon objects into a string storable in config table
+     *
+     * @param stdClass[] $emoticons array of emoticon objects
+     * @return string
+     */
+    public function encode_stored_config(
+        array $emoticons,
+    ): string {
+        return json_encode($emoticons);
+    }
+
+    /**
+     * Decodes the string into an array of emoticon objects
+     *
+     * @param string $encoded
+     * @return ?array
+     */
+    public function decode_stored_config(
+        string $encoded,
+    ): ?array {
+        $decoded = json_decode($encoded);
+        if (!is_array($decoded)) {
+            return null;
+        }
+        return $decoded;
+    }
+
+    /**
+     * Returns default set of emoticons supported by Moodle
+     *
+     * @return stdClass[] array of emoticon objects
+     */
+    public function default_emoticons(): array {
+        return [
+            $this->prepare_emoticon_object(":-)", 's/smiley', 'smiley'),
+            $this->prepare_emoticon_object(":)", 's/smiley', 'smiley'),
+            $this->prepare_emoticon_object(":-D", 's/biggrin', 'biggrin'),
+            $this->prepare_emoticon_object(";-)", 's/wink', 'wink'),
+            $this->prepare_emoticon_object(":-/", 's/mixed', 'mixed'),
+            $this->prepare_emoticon_object("V-.", 's/thoughtful', 'thoughtful'),
+            $this->prepare_emoticon_object(":-P", 's/tongueout', 'tongueout'),
+            $this->prepare_emoticon_object(":-p", 's/tongueout', 'tongueout'),
+            $this->prepare_emoticon_object("B-)", 's/cool', 'cool'),
+            $this->prepare_emoticon_object("^-)", 's/approve', 'approve'),
+            $this->prepare_emoticon_object("8-)", 's/wideeyes', 'wideeyes'),
+            $this->prepare_emoticon_object(":o)", 's/clown', 'clown'),
+            $this->prepare_emoticon_object(":-(", 's/sad', 'sad'),
+            $this->prepare_emoticon_object(":(", 's/sad', 'sad'),
+            $this->prepare_emoticon_object("8-.", 's/shy', 'shy'),
+            $this->prepare_emoticon_object(":-I", 's/blush', 'blush'),
+            $this->prepare_emoticon_object(":-X", 's/kiss', 'kiss'),
+            $this->prepare_emoticon_object("8-o", 's/surprise', 'surprise'),
+            $this->prepare_emoticon_object("P-|", 's/blackeye', 'blackeye'),
+            $this->prepare_emoticon_object("8-[", 's/angry', 'angry'),
+            $this->prepare_emoticon_object("(grr)", 's/angry', 'angry'),
+            $this->prepare_emoticon_object("xx-P", 's/dead', 'dead'),
+            $this->prepare_emoticon_object("|-.", 's/sleepy', 'sleepy'),
+            $this->prepare_emoticon_object("}-]", 's/evil', 'evil'),
+            $this->prepare_emoticon_object("(h)", 's/heart', 'heart'),
+            $this->prepare_emoticon_object("(heart)", 's/heart', 'heart'),
+            $this->prepare_emoticon_object("(y)", 's/yes', 'yes', 'core'),
+            $this->prepare_emoticon_object("(n)", 's/no', 'no', 'core'),
+            $this->prepare_emoticon_object("(martin)", 's/martin', 'martin'),
+            $this->prepare_emoticon_object("( )", 's/egg', 'egg'),
+        ];
+    }
+
+    /**
+     * Helper method preparing an emoticon object
+     *
+     * @param string|string[] $text
+     * @param string $imagename to be used by {@see pix_emoticon}
+     * @param ?string $altidentifier alternative string identifier, null for no alt
+     * @param string $altcomponent where the alternative string is defined
+     * @param string $imagecomponent to be used by {@see pix_emoticon}
+     * @return stdClass
+     */
+    protected function prepare_emoticon_object(
+        string|array $text,
+        string $imagename,
+        ?string $altidentifier = null,
+        string $altcomponent = 'core_pix',
+        string $imagecomponent = 'core',
+    ): stdClass {
+        return (object) [
+            'text' => $text,
+            'imagename' => $imagename,
+            'altidentifier' => $altidentifier,
+            'altcomponent' => $altcomponent,
+            'imagecomponent' => $imagecomponent,
+        ];
+    }
+}
+
+// Alias this class to the old name.
+// This file will be autoloaded by the legacyclasses autoload system.
+// In future all uses of this class will be corrected and the legacy references will be removed.
+class_alias(emoticon_manager::class, \emoticon_manager::class);
diff --git a/lib/db/legacyclasses.php b/lib/db/legacyclasses.php
index e1568603b03..7d049292dcf 100644
--- a/lib/db/legacyclasses.php
+++ b/lib/db/legacyclasses.php
@@ -33,6 +33,7 @@ $legacyclasses = [
     \bootstrap_renderer::class => 'output/bootstrap_renderer.php',
 
     // Core API.
+    \emoticon_manager::class => 'emoticon_manager.php',
     \lang_string::class => 'lang_string.php',
 
     // Exception API.
diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index d3c5d020fe0..e8aac00c089 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -7128,172 +7128,20 @@ function get_list_of_themes() {
 }
 
 /**
- * Factory function for emoticon_manager
+ * Factory function for {@see \core\emoticon_manager}
  *
- * @return emoticon_manager singleton
+ * @return \core\emoticon_manager singleton
  */
-function get_emoticon_manager() {
+function get_emoticon_manager(): \core\emoticon_manager {
     static $singleton = null;
 
     if (is_null($singleton)) {
-        $singleton = new emoticon_manager();
+        $singleton = new \core\emoticon_manager();
     }
 
     return $singleton;
 }
 
-/**
- * Provides core support for plugins that have to deal with emoticons (like HTML editor or emoticon filter).
- *
- * Whenever this manager mentiones 'emoticon object', the following data
- * structure is expected: stdClass with properties text, imagename, imagecomponent,
- * altidentifier and altcomponent
- *
- * @see admin_setting_emoticons
- *
- * @copyright 2010 David Mudrak
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-class emoticon_manager {
-
-    /**
-     * Returns the currently enabled emoticons
-     *
-     * @param boolean $selectable - If true, only return emoticons that should be selectable from a list.
-     * @return array of emoticon objects
-     */
-    public function get_emoticons($selectable = false) {
-        global $CFG;
-        $notselectable = ['martin', 'egg'];
-
-        if (empty($CFG->emoticons)) {
-            return array();
-        }
-
-        $emoticons = $this->decode_stored_config($CFG->emoticons);
-
-        if (!is_array($emoticons)) {
-            // Something is wrong with the format of stored setting.
-            debugging('Invalid format of emoticons setting, please resave the emoticons settings form', DEBUG_NORMAL);
-            return array();
-        }
-        if ($selectable) {
-            foreach ($emoticons as $index => $emote) {
-                if (in_array($emote->altidentifier, $notselectable)) {
-                    // Skip this one.
-                    unset($emoticons[$index]);
-                }
-            }
-        }
-
-        return $emoticons;
-    }
-
-    /**
-     * Converts emoticon object into renderable pix_emoticon object
-     *
-     * @param stdClass $emoticon emoticon object
-     * @param array $attributes explicit HTML attributes to set
-     * @return pix_emoticon
-     */
-    public function prepare_renderable_emoticon(stdClass $emoticon, array $attributes = array()) {
-        $stringmanager = get_string_manager();
-        if ($stringmanager->string_exists($emoticon->altidentifier, $emoticon->altcomponent)) {
-            $alt = get_string($emoticon->altidentifier, $emoticon->altcomponent);
-        } else {
-            $alt = s($emoticon->text);
-        }
-        return new pix_emoticon($emoticon->imagename, $alt, $emoticon->imagecomponent, $attributes);
-    }
-
-    /**
-     * Encodes the array of emoticon objects into a string storable in config table
-     *
-     * @see self::decode_stored_config()
-     * @param array $emoticons array of emtocion objects
-     * @return string
-     */
-    public function encode_stored_config(array $emoticons) {
-        return json_encode($emoticons);
-    }
-
-    /**
-     * Decodes the string into an array of emoticon objects
-     *
-     * @see self::encode_stored_config()
-     * @param string $encoded
-     * @return array|null
-     */
-    public function decode_stored_config($encoded) {
-        $decoded = json_decode($encoded);
-        if (!is_array($decoded)) {
-            return null;
-        }
-        return $decoded;
-    }
-
-    /**
-     * Returns default set of emoticons supported by Moodle
-     *
-     * @return array of sdtClasses
-     */
-    public function default_emoticons() {
-        return array(
-            $this->prepare_emoticon_object(":-)", 's/smiley', 'smiley'),
-            $this->prepare_emoticon_object(":)", 's/smiley', 'smiley'),
-            $this->prepare_emoticon_object(":-D", 's/biggrin', 'biggrin'),
-            $this->prepare_emoticon_object(";-)", 's/wink', 'wink'),
-            $this->prepare_emoticon_object(":-/", 's/mixed', 'mixed'),
-            $this->prepare_emoticon_object("V-.", 's/thoughtful', 'thoughtful'),
-            $this->prepare_emoticon_object(":-P", 's/tongueout', 'tongueout'),
-            $this->prepare_emoticon_object(":-p", 's/tongueout', 'tongueout'),
-            $this->prepare_emoticon_object("B-)", 's/cool', 'cool'),
-            $this->prepare_emoticon_object("^-)", 's/approve', 'approve'),
-            $this->prepare_emoticon_object("8-)", 's/wideeyes', 'wideeyes'),
-            $this->prepare_emoticon_object(":o)", 's/clown', 'clown'),
-            $this->prepare_emoticon_object(":-(", 's/sad', 'sad'),
-            $this->prepare_emoticon_object(":(", 's/sad', 'sad'),
-            $this->prepare_emoticon_object("8-.", 's/shy', 'shy'),
-            $this->prepare_emoticon_object(":-I", 's/blush', 'blush'),
-            $this->prepare_emoticon_object(":-X", 's/kiss', 'kiss'),
-            $this->prepare_emoticon_object("8-o", 's/surprise', 'surprise'),
-            $this->prepare_emoticon_object("P-|", 's/blackeye', 'blackeye'),
-            $this->prepare_emoticon_object("8-[", 's/angry', 'angry'),
-            $this->prepare_emoticon_object("(grr)", 's/angry', 'angry'),
-            $this->prepare_emoticon_object("xx-P", 's/dead', 'dead'),
-            $this->prepare_emoticon_object("|-.", 's/sleepy', 'sleepy'),
-            $this->prepare_emoticon_object("}-]", 's/evil', 'evil'),
-            $this->prepare_emoticon_object("(h)", 's/heart', 'heart'),
-            $this->prepare_emoticon_object("(heart)", 's/heart', 'heart'),
-            $this->prepare_emoticon_object("(y)", 's/yes', 'yes', 'core'),
-            $this->prepare_emoticon_object("(n)", 's/no', 'no', 'core'),
-            $this->prepare_emoticon_object("(martin)", 's/martin', 'martin'),
-            $this->prepare_emoticon_object("( )", 's/egg', 'egg'),
-        );
-    }
-
-    /**
-     * Helper method preparing the stdClass with the emoticon properties
-     *
-     * @param string|array $text or array of strings
-     * @param string $imagename to be used by {@link pix_emoticon}
-     * @param string $altidentifier alternative string identifier, null for no alt
-     * @param string $altcomponent where the alternative string is defined
-     * @param string $imagecomponent to be used by {@link pix_emoticon}
-     * @return stdClass
-     */
-    protected function prepare_emoticon_object($text, $imagename, $altidentifier = null,
-                                               $altcomponent = 'core_pix', $imagecomponent = 'core') {
-        return (object)array(
-            'text'           => $text,
-            'imagename'      => $imagename,
-            'imagecomponent' => $imagecomponent,
-            'altidentifier'  => $altidentifier,
-            'altcomponent'   => $altcomponent,
-        );
-    }
-}
-
 // ENVIRONMENT CHECKING.
 
 /**
diff --git a/lib/tests/emoticon_manager_test.php b/lib/tests/emoticon_manager_test.php
new file mode 100644
index 00000000000..c734fbf5e0f
--- /dev/null
+++ b/lib/tests/emoticon_manager_test.php
@@ -0,0 +1,123 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// 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;
+
+use advanced_testcase;
+use stdClass;
+use ReflectionMethod;
+
+/**
+ * Unit tests for emoticon manager
+ *
+ * @package     core
+ * @covers      \core\emoticon_manager
+ * @copyright   2024 Paul Holden <paulh@moodle.com>
+ * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+final class emoticon_manager_test extends advanced_testcase {
+
+    /**
+     * Data provider for {@see test_get_emoticons}
+     *
+     * @return array[]
+     */
+    public static function get_emoticons_provider(): array {
+        return [
+            'Only selectable' => [true, ['wink', 'biggrin'], ['egg', 'martin']],
+            'Including non-selectable' => [false, ['wink', 'biggrin', 'egg', 'martin']],
+        ];
+    }
+
+    /**
+     * Test getting enabled emoticons
+     *
+     * @param bool $selectable
+     * @param string[] $expected
+     * @param string[] $excluded
+     *
+     * @dataProvider get_emoticons_provider
+     */
+    public function test_get_emoticons(
+        bool $selectable,
+        array $expected,
+        array $excluded = [],
+    ): void {
+        $emoticons = (new emoticon_manager())->get_emoticons($selectable);
+        $identifiers = array_column($emoticons, 'altidentifier');
+
+        // Assert the subset of expected identifiers are all present.
+        $this->assertEquals([], array_diff($expected, $identifiers));
+
+        // Assert none of the excluded identifiers are present.
+        $this->assertEquals($excluded, array_diff($excluded, $identifiers));
+    }
+
+    /**
+     * Test converting emoticon object into renderable
+     */
+    public function test_prepare_renderable_emoticon(): void {
+        $manager = new emoticon_manager();
+
+        // With language string identifier.
+        $emoticon = $this->prepare_emoticon_object(':)', 's/smiley', 'smiley');
+        $pixemoticon = $manager->prepare_renderable_emoticon($emoticon);
+
+        $this->assertEquals('s/smiley', $pixemoticon->pix);
+        $this->assertEquals('core', $pixemoticon->component);
+        $this->assertEquals([
+            'class' => 'emoticon',
+            'alt' => 'smile',
+            'title' => 'smile',
+        ], $pixemoticon->attributes);
+
+        // With language string identifier from another component.
+        $emoticon = $this->prepare_emoticon_object(':)', 's/smiley', 'thanks', 'core');
+        $pixemoticon = $manager->prepare_renderable_emoticon($emoticon);
+
+        $this->assertEquals('s/smiley', $pixemoticon->pix);
+        $this->assertEquals('core', $pixemoticon->component);
+        $this->assertEquals([
+            'class' => 'emoticon',
+            'alt' => 'Thanks',
+            'title' => 'Thanks',
+        ], $pixemoticon->attributes);
+
+        // Without language string identifier.
+        $emoticon = $this->prepare_emoticon_object(':-O', 's/shock');
+        $pixemoticon = $manager->prepare_renderable_emoticon($emoticon);
+
+        $this->assertEquals('s/shock', $pixemoticon->pix);
+        $this->assertEquals('core', $pixemoticon->component);
+        $this->assertEquals([
+            'class' => 'emoticon',
+            'alt' => ':-O',
+            'title' => ':-O',
+        ], $pixemoticon->attributes);
+    }
+
+    /**
+     * Proxy method for creating emoticon object via {@see \core\emoticon_manager::prepare_emoticon_object}
+     *
+     * @param mixed ...$params
+     * @return stdClass
+     */
+    private function prepare_emoticon_object(...$params): stdClass {
+        $manager = new emoticon_manager();
+        $method = new ReflectionMethod($manager, 'prepare_emoticon_object');
+        return $method->invoke($manager, ...$params);
+    }
+}