diff --git a/src/Extend/Validator.php b/src/Extend/Validator.php
new file mode 100644
index 000000000..62301e93c
--- /dev/null
+++ b/src/Extend/Validator.php
@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Extend;
+
+use Flarum\Extension\Extension;
+use Illuminate\Contracts\Container\Container;
+
+class Validator implements ExtenderInterface
+{
+    private $configurationCallbacks = [];
+    private $validator;
+
+    /**
+     * @param string $validatorClass: The ::class attribute of the validator you are modifying.
+     *                                The validator should inherit from \Flarum\Foundation\AbstractValidator.
+     */
+    public function __construct($validatorClass)
+    {
+        $this->validator = $validatorClass;
+    }
+
+    /**
+     * Configure the validator. This is often used to adjust validation rules, but can be
+     * used to make other changes to the validator as well.
+     *
+     * @param callable $callable
+     *
+     * The callable can be a closure or invokable class, and should accept:
+     * - \Flarum\Foundation\AbstractValidator $flarumValidator: The Flarum validator wrapper
+     * - \Illuminate\Validation\Validator $validator: The Laravel validator instance
+     */
+    public function configure($callback)
+    {
+        $this->configurationCallbacks[] = $callback;
+
+        return $this;
+    }
+
+    public function extend(Container $container, Extension $extension = null)
+    {
+        $container->resolving($this->validator, function ($validator, $container) {
+            foreach ($this->configurationCallbacks as $callback) {
+                if (is_string($callback)) {
+                    $callback = $container->make($callback);
+                }
+
+                $validator->addConfiguration($callback);
+            }
+        });
+    }
+}
diff --git a/src/Foundation/AbstractValidator.php b/src/Foundation/AbstractValidator.php
index 37fff96bd..980558337 100644
--- a/src/Foundation/AbstractValidator.php
+++ b/src/Foundation/AbstractValidator.php
@@ -18,6 +18,16 @@ use Symfony\Component\Translation\TranslatorInterface;
 
 abstract class AbstractValidator
 {
+    /**
+     * @var array
+     */
+    protected $configuration = [];
+
+    public function addConfiguration($callable)
+    {
+        $this->configuration[] = $callable;
+    }
+
     /**
      * @var array
      */
@@ -92,10 +102,17 @@ abstract class AbstractValidator
 
         $validator = $this->validator->make($attributes, $rules, $this->getMessages());
 
+        /**
+         * @deprecated in beta 15, removed in beta 16.
+         */
         $this->events->dispatch(
             new Validating($this, $validator)
         );
 
+        foreach ($this->configuration as $callable) {
+            $callable($this, $validator);
+        }
+
         return $validator;
     }
 }
diff --git a/src/Foundation/Event/Validating.php b/src/Foundation/Event/Validating.php
index c8a6befcb..86c6d4cd3 100644
--- a/src/Foundation/Event/Validating.php
+++ b/src/Foundation/Event/Validating.php
@@ -13,6 +13,7 @@ use Flarum\Foundation\AbstractValidator;
 use Illuminate\Validation\Validator;
 
 /**
+ * @deprecated in Beta 15, remove in beta 16. Use the Validator extender instead.
  * The `Validating` event is called when a validator instance for a
  * model is being built. This event can be used to add custom rules/extensions
  * to the validator for when validation takes place.
diff --git a/tests/integration/extenders/ValidatorTest.php b/tests/integration/extenders/ValidatorTest.php
new file mode 100644
index 000000000..6a93e8bb6
--- /dev/null
+++ b/tests/integration/extenders/ValidatorTest.php
@@ -0,0 +1,97 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Tests\integration\extenders;
+
+use Flarum\Extend;
+use Flarum\Group\GroupValidator;
+use Flarum\Tests\integration\TestCase;
+use Flarum\User\UserValidator;
+use Illuminate\Validation\ValidationException;
+
+class ValidatorTest extends TestCase
+{
+    private function extendToRequireLongPassword()
+    {
+        $this->extend((new Extend\Validator(UserValidator::class))->configure(function ($flarumValidator, $validator) {
+            $validator->setRules([
+                'password' => [
+                    'required',
+                    'min:20'
+                ]
+            ] + $validator->getRules());
+        }));
+    }
+
+    private function extendToRequireLongPasswordViaInvokableClass()
+    {
+        $this->extend((new Extend\Validator(UserValidator::class))->configure(CustomValidatorClass::class));
+    }
+
+    /**
+     * @test
+     */
+    public function custom_validation_rule_does_not_exist_by_default()
+    {
+        $this->app()->getContainer()->make(UserValidator::class)->assertValid(['password' => 'simplePassword']);
+
+        // If we have gotten this far, no validation exception has been thrown, so the test is succesful.
+        $this->assertTrue(true);
+    }
+
+    /**
+     * @test
+     */
+    public function custom_validation_rule_exists_if_added()
+    {
+        $this->extendToRequireLongPassword();
+
+        $this->expectException(ValidationException::class);
+
+        $this->app()->getContainer()->make(UserValidator::class)->assertValid(['password' => 'simplePassword']);
+    }
+
+    /**
+     * @test
+     */
+    public function custom_validation_rule_exists_if_added_via_invokable_class()
+    {
+        $this->extendToRequireLongPasswordViaInvokableClass();
+
+        $this->expectException(ValidationException::class);
+
+        $this->app()->getContainer()->make(UserValidator::class)->assertValid(['password' => 'simplePassword']);
+    }
+
+    /**
+     * @test
+     */
+    public function custom_validation_rule_doesnt_affect_other_validators()
+    {
+        $this->extendToRequireLongPassword();
+
+        $this->app()->getContainer()->make(GroupValidator::class)->assertValid(['password' => 'simplePassword']);
+
+        // If we have gotten this far, no validation exception has been thrown, so the test is succesful.
+        $this->assertTrue(true);
+    }
+}
+
+class CustomValidatorClass
+{
+    public function __invoke($flarumValidator, $validator)
+    {
+        $validator->setRules([
+            'password' => [
+                'required',
+                'min:20'
+            ]
+        ] + $validator->getRules());
+    }
+}