styled-components is a popular JavaScript library for styling React components using tagged template literals and CSS-in-JS principles. It allows developers to write actual CSS code directly within their JavaScript, benefiting from component-level scope and dynamic styling based on props and theme contexts. This approach enhances code reusability and maintainability, reducing the common pitfalls of globally defined stylesheets. Styled-components helps streamline the process of styling React applications, offering cleaner and more manageable code.