This is of course a very hotly debated topic, and it is important to consider the various arguments for and against. On the one hand, Hamlet can be seen as treating Ophelia shamefully. One of the best examples of this is in Act III scene 1 whene he says "Get thee to a nunnery" and curses her. This would indicate very strongly that he does in fact not love her. In addition, he is willing to make fun of her and taunt her after this outburst in Act III scene 2 during his play that he has organised. However, it is important to remember with these scenes that it could be that Hamlet is aware of how Ophelia is being used against him by Claudius, and that he is being watched constantly. Therefore, it could be that these events are carefully staged demonstrations for the benefit of Claudius to deliberately confuse him. Hamlet, as a man who has wedded himself inexorably to revenge, is forced to sacrifice everything, even his love for Ophelia, in order to pursue his purpose.
No stronger evidence can be found in the play of Hamlet's love for Ophelia than in Act V scene 1, when Hamlet realises that the identity of the person whose grave is being dug is actually Ophelia herself. Note what he says as he bursts in on the funeral ceremony:
I loved Ophelia. Forty thousand brothersCould not with all their quantity of loveMake up my sum. What wilt thou do for her?