Ophelia is Polonius' daughter and Hamlet's former love interest. She and Hamlet are effectively boyfriend-girlfriend prior to the events of the story, but that relationship is quickly shattered. 

 Ophelia is stuck in a difficult place in the play. She can either stick with Hamlet and be disowned by her father or stay with her father and face a nasty breakup. She chooses the latter, and when Hamlet finds out that she's been spying on him for Polonius and Claudius, he attacks almost every part of her, and women in general.           

Ophelia has debatably the most tragic story of any of the characters in the play. In fact, by the final act of the play, she drives herself insane and (as is common in most tragedies) meets her end. Her story has entered the modern lexicon through Taylor Swift's song "The Fate of Ophelia," though her depiction of Ophelia is often criticized by musicians and scholars alike.

Ophelia and Hamlet together in the 1996 film