diff --git a/includes/base.inc b/includes/base.inc
index 2d2ceb5..e3f52c2 100644
--- a/includes/base.inc
+++ b/includes/base.inc
@@ -55,6 +55,16 @@ class views_object {
   function option_definition() { return array(); }
 
   /**
+   * Collect this handler's option definition and alter them, ready for use.
+   */
+  function altered_option_definition() {
+    $definition = $this->option_definition();
+    $type = !empty($this->is_plugin) ? 'plugin' : 'handler';
+    drupal_alter("views_{$type}_option_definition", $definition, $this);
+    return $definition;
+  }
+
+  /**
    * Views handlers use a special construct function so that we can more
    * easily construct them with variable arguments.
    */
@@ -74,7 +84,7 @@ class views_object {
    * feature that will likely disappear at some point.
    */
   function set_default_options() {
-    $this->_set_option_defaults($this->options, $this->option_definition());
+    $this->_set_option_defaults($this->options, $this->altered_option_definition());
 
     // Retained for complex defaults plus backward compatibility.
     $this->options($this->options);
@@ -105,7 +115,7 @@ class views_object {
     }
 
     if (!isset($definition)) {
-      $definition = $this->option_definition();
+      $definition = $this->altered_option_definition();
     }
 
     if (!empty($this->view)) {
@@ -202,7 +212,7 @@ class views_object {
 
   function export_options($indent, $prefix) {
     $output = '';
-    foreach ($this->option_definition() as $option => $definition) {
+    foreach ($this->altered_option_definition() as $option => $definition) {
       $output .= $this->export_option($indent, $prefix, $this->options, $option, $definition, array());
     }
 
@@ -274,7 +284,7 @@ class views_object {
    * Unpacks each handler to store translatable texts.
    */
   function unpack_translatables(&$translatable, $parents = array()) {
-    foreach ($this->option_definition() as $option => $definition) {
+    foreach ($this->altered_option_definition() as $option => $definition) {
       $this->unpack_translatable($translatable, $this->options, $option, $definition, $parents, array());
     }
   }
diff --git a/views.api.php b/views.api.php
index edbb03f..b0ccff9 100644
--- a/views.api.php
+++ b/views.api.php
@@ -712,6 +712,50 @@ function hook_views_plugins_alter(&$plugins) {
 }
 
 /**
+ * Alter existing plugin option definitions.
+ *
+ * This can be used to edit default or add new option definitions to existing
+ * plugins. The reason for doing this is that only overriding the relevent form
+ * with hook_form_alter() is insufficent because submitted form values will be
+ * removed if they haven't been declared as an available option.
+ *
+ * An alternative approach you could also take is to extend each plugin
+ * individually. However if your goal is to override many, or even all plugins,
+ * this results in a lot of additional code and files. This makes it a lot more
+ * troublesome to maintain the codebase, as well as interoperability with other
+ * modules.
+ *
+ * @see views_plugin_argument_default::option_definition()
+ * @see hook_views_handler_option_definition_alter()
+ * @see hook_form_alter()
+ */
+function hook_views_plugin_option_definition_alter(&$options, $plugin) {
+  $options['option_name'] = array('default' => '');
+}
+
+/**
+ * Alter existing handler option definitions.
+ *
+ * This can be used to edit default or add new option definitions to existing
+ * handers. The reason for doing this is that only overriding the relevent form
+ * with hook_form_alter() is insufficent because submitted form values will be
+ * removed if they haven't been declared as an available option.
+ *
+ * An alternative approach you could also take is to extend each handler
+ * individually. However if your goal is to override many, or even all handlers,
+ * this results in a lot of additional code and files. This makes it a lot more
+ * troublesome to maintain the codebase, as well as interoperability with other
+ * modules.
+ *
+ * @see views_handler::option_definition()
+ * @see hook_views_plugin_option_definition_alter()
+ * @see hook_form_alter()
+ */
+function hook_views_handler_option_definition_alter(&$options, $handler) {
+  $options['option_name'] = array('default' => '');
+}
+
+/**
  * Register View API information.
  *
  * This is required for your module to have its include files loaded; for