diff -u b/core/lib/Drupal/Core/CoreBundle.php b/core/lib/Drupal/Core/CoreBundle.php
--- b/core/lib/Drupal/Core/CoreBundle.php
+++ b/core/lib/Drupal/Core/CoreBundle.php
@@ -11,6 +11,7 @@
 use Drupal\Core\DependencyInjection\Compiler\RegisterMatchersPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterNestedMatchersPass;
 use Drupal\Core\DependencyInjection\Compiler\RegisterSerializationClassesPass;
+use Drupal\Core\DependencyInjection\Compiler\RegisterRouteLoadersPass;
 use Symfony\Component\DependencyInjection\Definition;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Reference;
@@ -73,8 +74,13 @@
     $container->register('router.builder', 'Drupal\Core\Routing\RouteBuilder')
       ->addArgument(new Reference('router.dumper'))
       ->addArgument(new Reference('lock'))
+      // Placeholder argument replaced with services tagged 'route_loader' by
+      // the RegisterRouteLoadersPass compiler pass.
+      ->addArgument(array())
       ->addArgument(new Reference('dispatcher'));
-
+    $container->register('router.loader.yaml', 'Drupal\Core\Routing\YamlRouteLoader')
+      ->addTag('route_loader');
+    $container->addCompilerPass(new RegisterRouteLoadersPass());
 
     $container->register('matcher', 'Drupal\Core\Routing\ChainMatcher');
     $container->register('legacy_url_matcher', 'Drupal\Core\LegacyUrlMatcher')
diff -u b/core/lib/Drupal/Core/Routing/RouteBuilder.php b/core/lib/Drupal/Core/Routing/RouteBuilder.php
--- b/core/lib/Drupal/Core/Routing/RouteBuilder.php
+++ b/core/lib/Drupal/Core/Routing/RouteBuilder.php
@@ -9,9 +9,7 @@
 
 use Symfony\Component\Routing\Matcher\Dumper\MatcherDumperInterface;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
-use Symfony\Component\Yaml\Parser;
 use Symfony\Component\Routing\RouteCollection;
-use Symfony\Component\Routing\Route;
 
 use Drupal\Core\Lock\LockBackendInterface;
 
@@ -38,6 +36,16 @@
   protected $lock;
 
   /**
+   * An array of \Drupal\Core\Routing\RouteLoaderInterface objects.
+   *
+   * During route rebuilding, each loader is invoked for each enabled Drupal
+   * module.
+   *
+   * @var array $loaders
+   */
+  protected $loaders;
+
+  /**
    * The event dispatcher to notify of routes.
    *
    * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface
@@ -51,12 +59,15 @@
    *   The matcher dumper used to store the route information.
    * @param \Drupal\Core\Lock\LockBackendInterface $lock
    *   The lock backend.
+   * @param array $loaders
+   *   An array of \Drupal\Core\Routing\RouteLoaderInterface objects.
    * @param \Symfony\Component\EventDispatcherEventDispatcherInterface
    *   The event dispatcher to notify of routes.
    */
-  public function __construct(MatcherDumperInterface $dumper, LockBackendInterface $lock, EventDispatcherInterface $dispatcher) {
+  public function __construct(MatcherDumperInterface $dumper, LockBackendInterface $lock, array $loaders, EventDispatcherInterface $dispatcher) {
     $this->dumper = $dumper;
     $this->lock = $lock;
+    $this->loaders = $loaders;
     $this->dispatcher = $dispatcher;
   }
 
@@ -72,38 +83,20 @@
       return;
     }
 
-    $parser = new Parser();
-
     // We need to manually call each module so that we can know which module
     // a given item came from.
     // @todo Use an injected Extension service rather than module_list():
     //   http://drupal.org/node/1331486.
     foreach (module_list() as $module) {
       $collection = new RouteCollection();
-      $routing_file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . '/' . $module . '.routing.yml';
-      if (file_exists($routing_file)) {
-        $routes = $parser->parse(file_get_contents($routing_file));
-        if (!empty($routes)) {
-          foreach ($routes as $name => $route_info) {
-            $defaults = isset($route_info['defaults']) ? $route_info['defaults'] : array();
-            $requirements = isset($route_info['requirements']) ? $route_info['requirements'] : array();
-            $route = new Route($route_info['pattern'], $defaults, $requirements);
-            $collection->add($name, $route);
-          }
-        }
+      foreach ($this->loaders as $loader) {
+        $collection->addCollection($loader->getRouteCollection($module));
       }
-      $this->dispatcher->dispatch(RoutingEvents::ALTER, new RouteBuildEvent($collection, $module));
+      $this->dispatcher->dispatch('routing.alter', new RouteBuildEvent($collection, $module));
       $this->dumper->addRoutes($collection);
       $this->dumper->dump(array('route_set' => $module));
     }
 
-    // Now allow modules to register additional, dynamic routes.
-    $collection = new RouteCollection();
-    $this->dispatcher->dispatch(RoutingEvents::DYNAMIC, new RouteBuildEvent($collection, 'dynamic_routes'));
-    $this->dispatcher->dispatch(RoutingEvents::ALTER, new RouteBuildEvent($collection, 'dynamic_routes'));
-    $this->dumper->addRoutes($collection);
-    $this->dumper->dump(array('route_set' => 'dynamic_routes'));
-
     $this->lock->release('router_rebuild');
   }
 
reverted:
--- b/core/lib/Drupal/Core/Routing/RoutingEvents.php
+++ /dev/null
@@ -1,38 +0,0 @@
-<?php
-
-/**
- * @file
- * Definition of \Drupal\Core\Routing\RoutingEvents.
- */
-
-namespace Drupal\Core\Routing;
-
-/**
- * Contains all events thrown in the core routing component.
- */
-final class RoutingEvents {
-
-  /**
-   * The ALTER event is fired on a route collection to allow changes to routes.
-   *
-   * This event is used to process new routes before they get saved.
-   *
-   * @see \Drupal\Core\Routing\RouteBuildEvent
-   *
-   * @var string
-   */
-  const ALTER = 'routing.route_alter';
-
-  /**
-   * The DYNAMIC event is fired to allow modules to register additional routes.
-   *
-   * Most routes are static, an should be defined as such. Dynamic routes are
-   * only those whose existence changes depending on the state of the system
-   * at runtime, depending on configuration.
-   *
-   * @see \Drupal\Core\Routing\RouteBuildEvent
-   *
-   * @var string
-   */
-  const DYNAMIC = 'routing.route_dynamic';
-}
diff -u b/core/update.php b/core/update.php
--- b/core/update.php
+++ b/core/update.php
@@ -460,6 +460,7 @@
 $container->register('router.builder', 'Drupal\Core\Routing\RouteBuilder')
   ->addArgument(new Reference('router.dumper'))
   ->addArgument(new Reference('lock'))
+  ->addArgument(array())
   ->addArgument(new Reference('dispatcher'));
 
 // Turn error reporting back on. From now on, only fatal errors (which are
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterRouteLoadersPass.php
@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\Core\DependencyInjection\Compiler\RegisterRouteLoadersPass.
+ */
+
+namespace Drupal\Core\DependencyInjection\Compiler;
+
+use Symfony\Component\DependencyInjection\Reference;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+
+/**
+ * Adds services tagged 'route_loader' to the route builder.
+ */
+class RegisterRouteLoadersPass implements CompilerPassInterface {
+
+  /**
+   * Adds services to the route builder.
+   *
+   * @param \Symfony\Component\DependencyInjection\ContainerBuilder $container
+   *   The container to process.
+   */
+  public function process(ContainerBuilder $container) {
+    $definition = $container->getDefinition('router.builder');
+
+    // Retrieve registered route loaders from the container.
+    foreach ($container->findTaggedServiceIds('route_loader') as $id => $attributes) {
+      $priority = isset($attributes[0]['priority']) ? $attributes[0]['priority'] : 0;
+      $loaders[$priority][] = new Reference($id);
+    }
+
+    // Add the registered loaders to the route builder as the 3rd argument.
+    if (!empty($loaders)) {
+      $definition->replaceArgument(2, $this->sort($loaders));
+    }
+  }
+
+  /**
+   * Sorts by priority.
+   *
+   * Order services from highest priority number to lowest (reverse sorting).
+   *
+   * @param array $services
+   *   A nested array keyed on priority number. For each priority number, the
+   *   value is an array of Symfony\Component\DependencyInjection\Reference
+   *   objects, each a reference to a route loader service.
+   *
+   * @return array
+   *   A flattened array of Reference objects from $services, ordered from high
+   *   to low priority.
+   */
+  protected function sort($services) {
+    $sorted = array();
+    krsort($services);
+
+    // Flatten the array.
+    foreach ($services as $a) {
+      $sorted = array_merge($sorted, $a);
+    }
+
+    return $sorted;
+  }
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/RouteLoaderInterface.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Routing\RouteLoaderInterface.
+ */
+
+namespace Drupal\Core\Routing;
+
+/**
+ * Interface for returning routes for a Drupal module.
+ */
+interface RouteLoaderInterface {
+
+  /**
+   * Returns routes for a given Drupal module.
+   *
+   * @param string $module
+   *   The Drupal module to load routes for.
+   *
+   * @return \Symfony\Component\Routing\RouteCollection
+   *   A RouteCollection.
+   */
+  public function getRouteCollection($module);
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/lib/Drupal/Core/Routing/YamlRouteLoader.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\Core\Routing\YamlRouteLoader.
+ */
+
+namespace Drupal\Core\Routing;
+
+use Symfony\Component\Yaml\Parser;
+use Symfony\Component\Routing\RouteCollection;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Loads routes from a module's MODULE.routing.yml file.
+ */
+class YamlRouteLoader {
+
+  /**
+   * Implements Drupal\Core\Routing\RouteLoaderInterface::getRouteCollection().
+   */
+  public function getRouteCollection($module) {
+    $parser = new Parser();
+    $collection = new RouteCollection();
+    $routing_file = DRUPAL_ROOT . '/' . drupal_get_path('module', $module) . '/' . $module . '.routing.yml';
+    if (file_exists($routing_file)) {
+      $routes = $parser->parse(file_get_contents($routing_file));
+      if (!empty($routes)) {
+        foreach ($routes as $name => $route_info) {
+          $defaults = isset($route_info['defaults']) ? $route_info['defaults'] : array();
+          $requirements = isset($route_info['requirements']) ? $route_info['requirements'] : array();
+          $route = new Route($route_info['pattern'], $defaults, $requirements);
+          $collection->add($name, $route);
+        }
+      }
+    }
+    return $collection;
+  }
+
+}