The role of a user interface (UI) designer is to create visually appealing and user-friendly interfaces for software applications and websites. UI designers focus on the layout, color schemes, typography, and interactive elements to enhance user experience. Their work involves ensuring that the design is intuitive, aesthetically pleasing, and aligns with the overall purpose of the application. Effective UI design is crucial in engaging users, facilitating navigation, and encouraging users to achieve their goals seamlessly.