diff --git a/blocks/api/categories.js b/blocks/api/categories.js
index 2a76e170cb378..f3f44f3c19fd7 100644
--- a/blocks/api/categories.js
+++ b/blocks/api/categories.js
@@ -1,3 +1,5 @@
+/* eslint no-console: [ 'error', { allow: [ 'error' ] } ] */
+
 /**
  * WordPress dependencies
  */
@@ -20,6 +22,14 @@ const categories = [
 	{ slug: 'reusable-blocks', title: __( 'Saved Blocks' ) },
 ];
 
+/**
+ * @type {RegExp}
+ * @const
+ *
+ * Category names must be a combination of lower-case letters, numbers, and hypens
+ */
+const categoryNamePattern = /^[a-z0-9-]+$/;
+
 /**
  * Returns all the block categories.
  *
@@ -28,3 +38,48 @@ const categories = [
 export function getCategories() {
 	return categories;
 }
+
+/**
+ * Register a new block Category.
+ *
+ * @param {Array} category e.g {slug: 'custom', title: __('Custom Blocks')}
+ *
+ * @return {Array} categories
+ */
+export function registerCategory( category ) {
+	if ( ! category ) {
+		console.error(
+			'The block Category must be defined'
+		);
+		return;
+	}
+	if ( ! category.slug ) {
+		console.error(
+			'The block Category slug must be defined'
+		);
+		return;
+	}
+	if ( ! categoryNamePattern.test( category.slug ) ) {
+		console.error(
+			'The block Category slug must not contain characters which are invalid for urls'
+		);
+		return;
+	}
+
+	if ( categories.some( x => x.slug === category.slug ) ) {
+		console.error(
+			'The block Category "' + category.slug + '" is already registered'
+		);
+		return;
+	}
+	if ( ! category.title ) {
+		console.error(
+			'The block Category title must be defined'
+		);
+		return;
+	}
+
+	categories.push( category );
+	return categories;
+}
+
diff --git a/blocks/api/index.js b/blocks/api/index.js
index 7f0653a133c5b..32d95bec5a6b1 100644
--- a/blocks/api/index.js
+++ b/blocks/api/index.js
@@ -8,7 +8,10 @@ export {
 	getSaveElement,
 } from './serializer';
 export { isValidBlock } from './validation';
-export { getCategories } from './categories';
+export {
+	getCategories,
+	registerCategory,
+} from './categories';
 export {
 	registerBlockType,
 	unregisterBlockType,
diff --git a/blocks/api/test/categories.js b/blocks/api/test/categories.js
new file mode 100644
index 0000000000000..f4e947f507b29
--- /dev/null
+++ b/blocks/api/test/categories.js
@@ -0,0 +1,69 @@
+/* eslint-disable no-console */
+
+/**
+ * External dependencies
+ */
+import { __ } from '@wordpress/i18n';
+
+/**
+ * Internal dependencies
+ */
+import {
+	registerCategory,
+} from '../categories';
+
+describe( 'categories', () => {
+	const error = console.error;
+
+	// Reset block state before each test.
+	beforeEach( () => {
+		console.error = jest.fn();
+	} );
+
+	afterEach( () => {
+		console.error = error;
+	} );
+
+	describe( 'registerCategory()', () => {
+		it( 'should reject empty categories', () => {
+			const categories = registerCategory();
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category must be defined' );
+			expect( categories ).toBeUndefined();
+		} );
+
+		it( 'should reject categories with empty slug', () => {
+			const categories = registerCategory( { slug: '', title: __( 'Custom Blocks' ) } );
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category slug must be defined' );
+			expect( categories ).toBeUndefined();
+		} );
+
+		it( 'should reject categories with slug not defined', () => {
+			const categories = registerCategory( { title: __( 'Custom Blocks' ) } );
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category slug must be defined' );
+			expect( categories ).toBeUndefined();
+		} );
+
+		it( 'should reject categories with invalid slug', () => {
+			const categories = registerCategory( { slug: 'custom blocks', title: __( 'Custom Blocks' ) } );
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category slug must not contain characters which are invalid for urls' );
+			expect( categories ).toBeUndefined();
+		} );
+
+		it( 'should reject categories with empty title', () => {
+			const categories = registerCategory( { slug: 'custom-blocks', title: '' } );
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category title must be defined' );
+			expect( categories ).toBeUndefined();
+		} );
+
+		it( 'should store the new category', () => {
+			const categories = registerCategory( { slug: 'custom-blocks', title: 'Custom Blocks' } );
+			expect( categories ).toEqual( jasmine.arrayContaining( [ { slug: 'custom-blocks', title: 'Custom Blocks' } ] ) );
+		} );
+
+		it( 'should reject categories already registered', () => {
+			const categories = registerCategory( { slug: 'custom-blocks', title: 'Custom Blocks' } );
+			expect( console.error ).toHaveBeenCalledWith( 'The block Category "custom-blocks" is already registered' );
+			expect( categories ).toBeUndefined();
+		} );
+	} );
+} );