diff --git a/lib/client-assets.php b/lib/client-assets.php
index b68c2fa5c99036..d8792b5fa2e963 100644
--- a/lib/client-assets.php
+++ b/lib/client-assets.php
@@ -1602,14 +1602,18 @@ function gutenberg_editor_scripts_and_styles( $hook ) {
 		'maxUploadFileSize'      => $max_upload_size,
 		'allowedMimeTypes'       => get_allowed_mime_types(),
 		'styles'                 => $styles,
-		'postLock'               => $lock_details,
 
 		// Ideally, we'd remove this and rely on a REST API endpoint.
+		'postLock'               => $lock_details,
 		'postLockUtils'          => array(
 			'nonce'       => wp_create_nonce( 'lock-post_' . $post->ID ),
 			'unlockNonce' => wp_create_nonce( 'update-post_' . $post->ID ),
 			'ajaxUrl'     => admin_url( 'admin-ajax.php' ),
 		),
+
+		// Whether or not to load the 'postcustom' meta box is stored as a user meta
+		// field so that we're not always loading its assets.
+		'enableCustomFields'     => (bool) get_user_meta( get_current_user_id(), 'enable_custom_fields', true ),
 	);
 
 	$post_autosave = gutenberg_get_autosave_newer_than_post_save( $post );
diff --git a/lib/meta-box-partial-page.php b/lib/meta-box-partial-page.php
index e50aaffb8c3a40..b77492bbbb87ac 100644
--- a/lib/meta-box-partial-page.php
+++ b/lib/meta-box-partial-page.php
@@ -113,7 +113,6 @@ function gutenberg_filter_meta_boxes( $meta_boxes ) {
 	$core_normal_meta_boxes = array(
 		'revisionsdiv',
 		'postexcerpt',
-		'postcustom',
 		'trackbacksdiv',
 		'commentstatusdiv',
 		'commentsdiv',
@@ -121,6 +120,13 @@ function gutenberg_filter_meta_boxes( $meta_boxes ) {
 		'authordiv',
 	);
 
+	// Whether or not to load the 'postcustom' meta box is stored as a user meta
+	// field so that we're not always loading its assets.
+	$enable_custom_fields = (bool) get_user_meta( get_current_user_id(), 'enable_custom_fields', true );
+	if ( ! $enable_custom_fields ) {
+		$core_normal_meta_boxes[] = 'postcustom';
+	}
+
 	$taxonomy_callbacks_to_unset = array(
 		'post_tags_meta_box',
 		'post_categories_meta_box',
@@ -298,6 +304,10 @@ function the_gutenberg_metaboxes() {
 	<form class="metabox-base-form">
 	<?php gutenberg_meta_box_post_form_hidden_fields( $post ); ?>
 	</form>
+	<form id="toggle-custom-fields-form" method="post" action="<?php echo esc_attr( admin_url( 'admin-post.php' ) ); ?>">
+		<?php wp_nonce_field( 'toggle_custom_fields' ); ?>
+		<input type="hidden" name="action" value="toggle_custom_fields" />
+	</form>
 	<?php foreach ( $locations as $location ) : ?>
 		<form class="metabox-location-<?php echo esc_attr( $location ); ?>">
 			<div id="poststuff" class="sidebar-open">
@@ -359,6 +369,30 @@ function the_gutenberg_metaboxes() {
 		printf( "<script type='text/javascript'>\n%s\n</script>\n", trim( $script ) );
 	}
 
+	/**
+	 * If the 'postcustom' meta box is enabled, then we need to perform some
+	 * extra initialization on it.
+	 */
+	$enable_custom_fields = (bool) get_user_meta( get_current_user_id(), 'enable_custom_fields', true );
+	if ( $enable_custom_fields ) {
+		$script = "( function( $ ) {
+			if ( $('#postcustom').length ) {
+				$( '#the-list' ).wpList( {
+					addBefore: function( s ) {
+						s.data += '&post_id=$post->ID';
+						return s;
+					},
+					addAfter: function() {
+						$('table#list-table').show();
+					}
+				});
+			}
+		} )( jQuery );";
+
+		wp_enqueue_script( 'wp-lists' );
+		wp_add_inline_script( 'wp-lists', $script );
+	}
+
 	// Reset meta box data.
 	$wp_meta_boxes = $_original_meta_boxes;
 }
@@ -402,3 +436,25 @@ function gutenberg_meta_box_post_form_hidden_fields( $post ) {
 	// Permalink title nonce.
 	wp_nonce_field( 'samplepermalink', 'samplepermalinknonce', false );
 }
+
+/**
+ * Admin action which toggles the 'enable_custom_fields' option, then redirects
+ * back to the editor. This allows Gutenberg to render a control that lets the
+ * user to completely enable or disable the 'postcustom' meta box.
+ *
+ * @since 5.2.0
+ */
+function gutenberg_toggle_custom_fields() {
+	check_admin_referer( 'toggle_custom_fields' );
+
+	$current_user_id = get_current_user_id();
+	if ( $current_user_id ) {
+		$enable_custom_fields = (bool) get_user_meta( $current_user_id, 'enable_custom_fields', true );
+		update_user_meta( $current_user_id, 'enable_custom_fields', ! $enable_custom_fields );
+	}
+
+	wp_safe_redirect( wp_get_referer() );
+	exit;
+}
+
+add_action( 'admin_post_toggle_custom_fields', 'gutenberg_toggle_custom_fields' );
diff --git a/packages/edit-post/src/components/options-modal/index.js b/packages/edit-post/src/components/options-modal/index.js
index 16342d851056c7..2206847f19d590 100644
--- a/packages/edit-post/src/components/options-modal/index.js
+++ b/packages/edit-post/src/components/options-modal/index.js
@@ -1,7 +1,7 @@
 /**
  * External dependencies
  */
-import { get, map } from 'lodash';
+import { get } from 'lodash';
 
 /**
  * WordPress dependencies
@@ -16,11 +16,16 @@ import { PostTaxonomies, PostExcerptCheck, PageAttributesCheck } from '@wordpres
  * Internal dependencies
  */
 import Section from './section';
-import { EnablePublishSidebarOption, EnableTipsOption, EnablePanelOption } from './options';
+import {
+	EnablePublishSidebarOption,
+	EnableTipsOption,
+	EnablePanelOption,
+} from './options';
+import MetaBoxesSection from './meta-boxes-section';
 
 const MODAL_NAME = 'edit-post/options';
 
-export function OptionsModal( { isModalActive, closeModal, metaBoxes = [] } ) {
+export function OptionsModal( { isModalActive, closeModal } ) {
 	if ( ! isModalActive ) {
 		return null;
 	}
@@ -54,13 +59,7 @@ export function OptionsModal( { isModalActive, closeModal, metaBoxes = [] } ) {
 					<EnablePanelOption label={ __( 'Page Attributes' ) } panelName="page-attributes" />
 				</PageAttributesCheck>
 			</Section>
-			{ metaBoxes.length !== 0 && (
-				<Section title={ __( 'Advanced Panels' ) }>
-					{ map( metaBoxes, ( { title, id } ) => (
-						<EnablePanelOption key={ id } label={ title } panelName={ `meta-box-${ id }` } />
-					) ) }
-				</Section>
-			) }
+			<MetaBoxesSection title={ __( 'Advanced Panels' ) } />
 		</Modal>
 	);
 }
@@ -68,7 +67,6 @@ export function OptionsModal( { isModalActive, closeModal, metaBoxes = [] } ) {
 export default compose(
 	withSelect( ( select ) => ( {
 		isModalActive: select( 'core/edit-post' ).isModalActive( MODAL_NAME ),
-		metaBoxes: select( 'core/edit-post' ).getAllMetaBoxes(),
 	} ) ),
 	withDispatch( ( dispatch ) => {
 		return {
diff --git a/packages/edit-post/src/components/options-modal/meta-boxes-section.js b/packages/edit-post/src/components/options-modal/meta-boxes-section.js
new file mode 100644
index 00000000000000..414ed37d34b010
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/meta-boxes-section.js
@@ -0,0 +1,50 @@
+/**
+ * External dependencies
+ */
+import { map } from 'lodash';
+
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { withSelect } from '@wordpress/data';
+
+/**
+ * Internal dependencies
+ */
+import Section from './section';
+import { EnableCustomFieldsOption, EnablePanelOption } from './options';
+
+function MetaBoxesSection( { hasCustomFieldsSupport, metaBoxes, ...sectionProps } ) {
+	if ( ! hasCustomFieldsSupport && metaBoxes.length === 0 ) {
+		return null;
+	}
+
+	return (
+		<Section { ...sectionProps }>
+			{ hasCustomFieldsSupport && (
+				<EnableCustomFieldsOption label={ __( 'Custom Fields' ) } />
+			) }
+			{ map(
+				metaBoxes,
+				( { id, title } ) =>
+					// The 'Custom Fields' meta box is a special case handled above.
+					id !== 'postcustom' && (
+						<EnablePanelOption key={ id } label={ title } panelName={ `meta-box-${ id }` } />
+					)
+			) }
+		</Section>
+	);
+}
+
+export default withSelect( ( select ) => {
+	const { getEditedPostAttribute } = select( 'core/editor' );
+	const { getPostType } = select( 'core' );
+	const { getAllMetaBoxes } = select( 'core/edit-post' );
+
+	const postType = getPostType( getEditedPostAttribute( 'type' ) );
+	return {
+		hasCustomFieldsSupport: postType.supports[ 'custom-fields' ],
+		metaBoxes: getAllMetaBoxes(),
+	};
+} )( MetaBoxesSection );
diff --git a/packages/edit-post/src/components/options-modal/options.js b/packages/edit-post/src/components/options-modal/options.js
deleted file mode 100644
index 7f9cd5845c9685..00000000000000
--- a/packages/edit-post/src/components/options-modal/options.js
+++ /dev/null
@@ -1,85 +0,0 @@
-/**
- * WordPress dependencies
- */
-import { CheckboxControl } from '@wordpress/components';
-import { Component } from '@wordpress/element';
-import { compose } from '@wordpress/compose';
-import { withSelect, withDispatch } from '@wordpress/data';
-import { ifViewportMatches } from '@wordpress/viewport';
-
-function Option( { label, isChecked, onChange } ) {
-	return (
-		<CheckboxControl
-			className="edit-post-options-modal__option"
-			label={ label }
-			checked={ isChecked }
-			onChange={ onChange }
-		/>
-	);
-}
-
-class DeferredOption extends Component {
-	constructor( { isChecked } ) {
-		super( ...arguments );
-		this.state = {
-			isChecked,
-		};
-	}
-
-	componentWillUnmount() {
-		if ( this.state.isChecked !== this.props.isChecked ) {
-			this.props.onChange( this.state.isChecked );
-		}
-	}
-
-	render() {
-		return (
-			<Option
-				label={ this.props.label }
-				isChecked={ this.state.isChecked }
-				onChange={ ( isChecked ) => this.setState( { isChecked } ) }
-			/>
-		);
-	}
-}
-
-export const EnablePublishSidebarOption = compose(
-	withSelect( ( select ) => ( {
-		isChecked: select( 'core/editor' ).isPublishSidebarEnabled(),
-	} ) ),
-	withDispatch( ( dispatch ) => {
-		const { enablePublishSidebar, disablePublishSidebar } = dispatch( 'core/editor' );
-		return {
-			onChange: ( isEnabled ) => ( isEnabled ? enablePublishSidebar() : disablePublishSidebar() ),
-		};
-	} ),
-	// In < medium viewports we override this option and always show the publish sidebar.
-	// See the edit-post's header component for the specific logic.
-	ifViewportMatches( 'medium' ),
-)( Option );
-
-export const EnableTipsOption = compose(
-	withSelect( ( select ) => ( {
-		isChecked: select( 'core/nux' ).areTipsEnabled(),
-	} ) ),
-	withDispatch( ( dispatch ) => {
-		const { enableTips, disableTips } = dispatch( 'core/nux' );
-		return {
-			onChange: ( isEnabled ) => ( isEnabled ? enableTips() : disableTips() ),
-		};
-	} )
-)(
-	// Using DeferredOption here means enableTips() is called when the Options
-	// modal is dismissed. This stops the NUX guide from appearing above the
-	// Options modal, which looks totally weird.
-	DeferredOption
-);
-
-export const EnablePanelOption = compose(
-	withSelect( ( select, { panelName } ) => ( {
-		isChecked: select( 'core/edit-post' ).isEditorPanelEnabled( panelName ),
-	} ) ),
-	withDispatch( ( dispatch, { panelName } ) => ( {
-		onChange: () => dispatch( 'core/edit-post' ).toggleEditorPanelEnabled( panelName ),
-	} ) )
-)( Option );
diff --git a/packages/edit-post/src/components/options-modal/options/base.js b/packages/edit-post/src/components/options-modal/options/base.js
new file mode 100644
index 00000000000000..1dd5b9d013af0f
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/base.js
@@ -0,0 +1,17 @@
+/**
+ * WordPress dependencies
+ */
+import { CheckboxControl } from '@wordpress/components';
+
+function BaseOption( { label, isChecked, onChange } ) {
+	return (
+		<CheckboxControl
+			className="edit-post-options-modal__option"
+			label={ label }
+			checked={ isChecked }
+			onChange={ onChange }
+		/>
+	);
+}
+
+export default BaseOption;
diff --git a/packages/edit-post/src/components/options-modal/options/deferred.js b/packages/edit-post/src/components/options-modal/options/deferred.js
new file mode 100644
index 00000000000000..2a0f84348d23bb
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/deferred.js
@@ -0,0 +1,36 @@
+/**
+ * WordPress dependencies
+ */
+import { Component } from '@wordpress/element';
+
+/**
+ * Internal dependencies
+ */
+import BaseOption from './base';
+
+class DeferredOption extends Component {
+	constructor( { isChecked } ) {
+		super( ...arguments );
+		this.state = {
+			isChecked,
+		};
+	}
+
+	componentWillUnmount() {
+		if ( this.state.isChecked !== this.props.isChecked ) {
+			this.props.onChange( this.state.isChecked );
+		}
+	}
+
+	render() {
+		return (
+			<BaseOption
+				label={ this.props.label }
+				isChecked={ this.state.isChecked }
+				onChange={ ( isChecked ) => this.setState( { isChecked } ) }
+			/>
+		);
+	}
+}
+
+export default DeferredOption;
diff --git a/packages/edit-post/src/components/options-modal/options/enable-custom-fields.js b/packages/edit-post/src/components/options-modal/options/enable-custom-fields.js
new file mode 100644
index 00000000000000..a22f96250ccadc
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/enable-custom-fields.js
@@ -0,0 +1,47 @@
+/**
+ * WordPress dependencies
+ */
+import { Component } from '@wordpress/element';
+import { withSelect } from '@wordpress/data';
+
+/**
+ * Internal dependencies
+ */
+import BaseOption from './base';
+
+class EnableCustomFieldsOption extends Component {
+	constructor( { isChecked } ) {
+		super( ...arguments );
+
+		this.toggleCustomFields = this.toggleCustomFields.bind( this );
+
+		this.state = { isChecked };
+	}
+
+	toggleCustomFields() {
+		// Submit a hidden form which triggers the toggle_custom_fields admin action.
+		// This action will toggle the setting and reload the editor with the meta box
+		// assets included on the page.
+		document.getElementById( 'toggle-custom-fields-form' ).submit();
+
+		// Make it look like something happened while the page reloads.
+		this.setState( { isChecked: ! this.props.isChecked } );
+	}
+
+	render() {
+		const { label } = this.props;
+		const { isChecked } = this.state;
+
+		return (
+			<BaseOption
+				label={ label }
+				isChecked={ isChecked }
+				onChange={ this.toggleCustomFields }
+			/>
+		);
+	}
+}
+
+export default withSelect( ( select ) => ( {
+	isChecked: select( 'core/editor' ).getEditorSettings().enableCustomFields,
+} ) )( EnableCustomFieldsOption );
diff --git a/packages/edit-post/src/components/options-modal/options/enable-panel.js b/packages/edit-post/src/components/options-modal/options/enable-panel.js
new file mode 100644
index 00000000000000..d21f1051cb039f
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/enable-panel.js
@@ -0,0 +1,19 @@
+/**
+ * WordPress dependencies
+ */
+import { compose } from '@wordpress/compose';
+import { withSelect, withDispatch } from '@wordpress/data';
+
+/**
+ * Internal dependencies
+ */
+import BaseOption from './base';
+
+export default compose(
+	withSelect( ( select, { panelName } ) => ( {
+		isChecked: select( 'core/edit-post' ).isEditorPanelEnabled( panelName ),
+	} ) ),
+	withDispatch( ( dispatch, { panelName } ) => ( {
+		onChange: () => dispatch( 'core/edit-post' ).toggleEditorPanelEnabled( panelName ),
+	} ) )
+)( BaseOption );
diff --git a/packages/edit-post/src/components/options-modal/options/enable-publish-sidebar.js b/packages/edit-post/src/components/options-modal/options/enable-publish-sidebar.js
new file mode 100644
index 00000000000000..e080fae5781274
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/enable-publish-sidebar.js
@@ -0,0 +1,26 @@
+/**
+ * WordPress dependencies
+ */
+import { compose } from '@wordpress/compose';
+import { withSelect, withDispatch } from '@wordpress/data';
+import { ifViewportMatches } from '@wordpress/viewport';
+
+/**
+ * Internal dependencies
+ */
+import BaseOption from './base';
+
+export default compose(
+	withSelect( ( select ) => ( {
+		isChecked: select( 'core/editor' ).isPublishSidebarEnabled(),
+	} ) ),
+	withDispatch( ( dispatch ) => {
+		const { enablePublishSidebar, disablePublishSidebar } = dispatch( 'core/editor' );
+		return {
+			onChange: ( isEnabled ) => ( isEnabled ? enablePublishSidebar() : disablePublishSidebar() ),
+		};
+	} ),
+	// In < medium viewports we override this option and always show the publish sidebar.
+	// See the edit-post's header component for the specific logic.
+	ifViewportMatches( 'medium' ),
+)( BaseOption );
diff --git a/packages/edit-post/src/components/options-modal/options/enable-tips.js b/packages/edit-post/src/components/options-modal/options/enable-tips.js
new file mode 100644
index 00000000000000..8771f8437ba53a
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/enable-tips.js
@@ -0,0 +1,27 @@
+/**
+ * WordPress dependencies
+ */
+import { compose } from '@wordpress/compose';
+import { withSelect, withDispatch } from '@wordpress/data';
+
+/**
+ * Internal dependencies
+ */
+import DeferredOption from './deferred';
+
+export default compose(
+	withSelect( ( select ) => ( {
+		isChecked: select( 'core/nux' ).areTipsEnabled(),
+	} ) ),
+	withDispatch( ( dispatch ) => {
+		const { enableTips, disableTips } = dispatch( 'core/nux' );
+		return {
+			onChange: ( isEnabled ) => ( isEnabled ? enableTips() : disableTips() ),
+		};
+	} )
+)(
+	// Using DeferredOption here means enableTips() is called when the Options
+	// modal is dismissed. This stops the NUX guide from appearing above the
+	// Options modal, which looks totally weird.
+	DeferredOption
+);
diff --git a/packages/edit-post/src/components/options-modal/options/index.js b/packages/edit-post/src/components/options-modal/options/index.js
new file mode 100644
index 00000000000000..7961206caba4ed
--- /dev/null
+++ b/packages/edit-post/src/components/options-modal/options/index.js
@@ -0,0 +1,4 @@
+export { default as EnableCustomFieldsOption } from './enable-custom-fields';
+export { default as EnablePanelOption } from './enable-panel';
+export { default as EnablePublishSidebarOption } from './enable-publish-sidebar';
+export { default as EnableTipsOption } from './enable-tips';
diff --git a/packages/edit-post/src/components/options-modal/test/__snapshots__/index.js.snap b/packages/edit-post/src/components/options-modal/test/__snapshots__/index.js.snap
index 826f329f242dfa..67df8a5bd60893 100644
--- a/packages/edit-post/src/components/options-modal/test/__snapshots__/index.js.snap
+++ b/packages/edit-post/src/components/options-modal/test/__snapshots__/index.js.snap
@@ -15,7 +15,7 @@ exports[`OptionsModal should match snapshot when the modal is active 1`] = `
   <Section
     title="General"
   >
-    <WithSelect(WithDispatch(IfViewportMatches(Option)))
+    <WithSelect(WithDispatch(IfViewportMatches(BaseOption)))
       label="Enable Pre-publish Checks"
     />
     <WithSelect(WithDispatch(DeferredOption))
@@ -28,26 +28,29 @@ exports[`OptionsModal should match snapshot when the modal is active 1`] = `
     <WithSelect(PostTaxonomies)
       taxonomyWrapper={[Function]}
     />
-    <WithSelect(WithDispatch(Option))
+    <WithSelect(WithDispatch(BaseOption))
       label="Featured Image"
       panelName="featured-image"
     />
     <PostExcerptCheck>
-      <WithSelect(WithDispatch(Option))
+      <WithSelect(WithDispatch(BaseOption))
         label="Excerpt"
         panelName="post-excerpt"
       />
     </PostExcerptCheck>
-    <WithSelect(WithDispatch(Option))
+    <WithSelect(WithDispatch(BaseOption))
       label="Discussion"
       panelName="discussion-panel"
     />
     <WithSelect(PageAttributesCheck)>
-      <WithSelect(WithDispatch(Option))
+      <WithSelect(WithDispatch(BaseOption))
         label="Page Attributes"
         panelName="page-attributes"
       />
     </WithSelect(PageAttributesCheck)>
   </Section>
+  <WithSelect(MetaBoxesSection)
+    title="Advanced Panels"
+  />
 </WithInstanceId(Modal)>
 `;
diff --git a/test/e2e/specs/nux.test.js b/test/e2e/specs/nux.test.js
index e18788218e546d..8702587f6b55b7 100644
--- a/test/e2e/specs/nux.test.js
+++ b/test/e2e/specs/nux.test.js
@@ -87,16 +87,12 @@ describe( 'New User Experience (NUX)', () => {
 		expect( nuxTipElements ).toHaveLength( 0 );
 	} );
 
-	it( 'should toggle tips when the "Enable tips" option is toggled', async () => {
-		// Tips should be enabled at first.
-		let nuxTipElements = await page.$$( '.nux-dot-tip' );
-		expect( nuxTipElements ).toHaveLength( 1 );
-
-		// Toggle the 'Enable Tips' option to disable.
-		await toggleOption( 'Enable Tips' );
+	it( 'should enable tips when the "Enable tips" option is toggled on', async () => {
+		// Start by disabling tips.
+		await page.click( '.nux-dot-tip__disable' );
 
-		// Should disable tips from appearing.
-		nuxTipElements = await page.$$( '.nux-dot-tip' );
+		// Verify no more tips are visible on the page.
+		let nuxTipElements = await page.$$( '.nux-dot-tip' );
 		expect( nuxTipElements ).toHaveLength( 0 );
 
 		// Tips should be disabled in localStorage as well.