The significance of a user persona in UX design lies in its role in guiding the design process to create user-centered products. A user persona represents a fictional character that embodies the characteristics, needs, and motivations of a target user group. By utilizing user personas, designers can better understand user behavior, preferences, and pain points, leading to informed decisions in layout, functionality, and usability. This ultimately enhances the user experience and ensures that the product meets real user expectations.