Teseo ("Theseus", HWV 9; Italian pronunciation: [teˈzɛo]) is an opera seria with music by George Frideric Handel, the only Handel opera that is in five acts. The Italian-language libretto was by Nicola Francesco Haym, after Philippe Quinault's Thésée. It was Handel's third London opera, intended to follow the success of Rinaldo after the unpopular Il pastor fido.

First performed on 10 January 1713,Teseo featured "magical" effects such as flying dragons, transformation scenes and apparitions and had a cast of notable Italian opera singers. It was a success with London audiences, receiving thirteen performances even though the stage machinery for the "magical" effects broke down, and would have received more performances had not one of the theatre's managers run away with the box office receipts.