User interface (UI) design influences software usability by determining how intuitive and efficient the interaction between user and software is. Effective UI design includes clear navigation, responsive elements, and a logical layout to guide users smoothly through tasks. A well-designed interface reduces cognitive load, making software accessible even to non-technical users. Visual elements, such as typography and color schemes, also play a vital role in creating a pleasant user experience. Ultimately, thoughtful UI design enhances satisfaction, encourages usage, and can significantly impact overall software success.