diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3adee70813c..fdd9dc589cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -157,6 +157,7 @@
 - Added `CraftCms\Cms\Element\Data\ElementSiteSettings`, the shared base for element URI and route settings. ([#19762](https://github.com/craftcms/cms/pull/19762))
 - Added support for fluent plugin settings classes. ([#19574](https://github.com/craftcms/cms/pull/19574))
 - Added support for refreshable standard plugin settings forms and conditional configuration of core form nodes. ([#19545](https://github.com/craftcms/cms/pull/19545))
+- Added `CraftCms\Cms\Form\Nodes\Group::expanded()`, allowing collapsible section groups to start expanded in Vue and HTML forms. ([#19772](https://github.com/craftcms/cms/pull/19772))
 - Added `CraftCms\Cms\Route\CurrentElement`, a contextual attribute for injecting the matched element into controller actions and route closures. ([#19762](https://github.com/craftcms/cms/pull/19762))
 - Added `CraftCms\Cms\Contracts\PluginInterface::createSettings()`, which replaces `createSettingsModel()`. ([#19574](https://github.com/craftcms/cms/pull/19574))
 - Added `CraftCms\Cms\Dashboard\Widgets\Widget::component()` and `props()`, which replace `getBodyHtml()`. ([#19564](https://github.com/craftcms/cms/pull/19564))
diff --git a/resources/js/modules/forms/GroupNode.vue b/resources/js/modules/forms/GroupNode.vue
index a5dae93d583..fac771b964e 100644
--- a/resources/js/modules/forms/GroupNode.vue
+++ b/resources/js/modules/forms/GroupNode.vue
@@ -13,6 +13,7 @@
   type GroupNodeProps = {
     label?: string | null;
     collapsible?: boolean;
+    expanded?: boolean;
     /** Renders the group as one field rather than a section — see `Nodes\Group`. */
     asField?: boolean;
     required?: boolean;
@@ -104,6 +105,9 @@
     v-else
     :is="node.props.collapsible ? 'craft-disclosure' : 'fieldset'"
     :label="node.props.collapsible ? node.props.label : undefined"
+    .opened="
+      node.props.collapsible ? (node.props.expanded ?? false) : undefined
+    "
     :class="{
       [`width-${node.props.width}`]: Boolean(node.props.width),
       hidden: Boolean(node.props.hidden),
diff --git a/src/Form/Nodes/Group.php b/src/Form/Nodes/Group.php
index fd1fd030b44..c5b2093e16b 100644
--- a/src/Form/Nodes/Group.php
+++ b/src/Form/Nodes/Group.php
@@ -49,6 +49,8 @@ class Group extends Container
 
     private bool $collapsible = false;
 
+    private bool $expanded = false;
+
     private bool $asField = false;
 
     private bool $required = false;
@@ -87,6 +89,7 @@ public static function renderHtml(NodePayload $node, FormPayload $payload, FormH
         if ($node->props['collapsible'] ?? false) {
             return Html::tag('craft-disclosure', $children->toHtml(), [
                 'label' => $label,
+                'opened' => $node->props['expanded'] ?? false,
                 ...$attributes,
             ]);
         }
@@ -115,6 +118,14 @@ public function collapsible(bool $collapsible = true): static
         return $this;
     }
 
+    /** Section appearance only; ignored unless the group is {@see self::collapsible()}. */
+    public function expanded(bool $expanded = true): static
+    {
+        $this->expanded = $expanded;
+
+        return $this;
+    }
+
     /**
      * Renders the group as one field rather than a section — see the class
      * docblock. Takes precedence over {@see self::collapsible()}.
@@ -194,6 +205,7 @@ public function props(): array
         return [
             'label' => $this->label,
             ...($this->collapsible && ! $this->asField ? ['collapsible' => true] : []),
+            ...($this->collapsible && ! $this->asField && $this->expanded ? ['expanded' => true] : []),
             ...($this->asField ? ['asField' => true] : []),
             ...($this->asField && $this->required ? ['required' => true] : []),
             ...Arr::whereNotNull([