Atomize by Quarkly - Library for creating atomic react components
Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions
Ant Design - An enterprise-class UI design language and React implementation with a set of high-quality React components, one of best React UI library for enterprises
Materialize CSS - A modern responsive front-end framework based on Material Design
Bulma - Bulma is an open source CSS framework based on Flexbox and built with Sass. It's 100% responsive, fully modular, and available for free.
Tailwind CSS - A utility-first CSS framework for rapidly building custom user interfaces.