Rosaline () is a fictional character mentioned in William Shakespeare's tragedy Romeo and Juliet. She is the niece of Lord Capulet. Although an unseen character, her role is important: Romeo's unrequited love for Rosaline leads him to try to catch a glimpse of her at a gathering hosted by the Capulet family, during which he first spots her cousin, Juliet. Scholars generally compare Romeo's short-lived love of Rosaline with his later love of Juliet. The poetry Shakespeare writes for Rosaline is much weaker than that for Juliet.
https://en.wikipedia.org/wiki/Rosaline