Alessandro (Alexander the Great, HWV 21) is an opera written for the Royal Academy of Music (1719) composed by George Frideric Handel in 1726. Paolo Rolli was the librettist and based the story on Ortensio Mauro's La superbia d'Alessandro. This was the first opera where Handel had cast together in the same opera the famous singers Faustina Bordoni, as Rossane, and Francesca Cuzzoni, as Lisaura. Handel made use of their real-life professional rivalry in his treatment of the story. The original cast also included Francesco Bernardi ("Senesino").

Handel had originally planned Alessandro to be his first contribution to the 1725/1726 season of the Royal Academy. However, Bordoni did not arrive in London in time to stage Alessandro, and Handel substituted his own Scipione in March and April 1726 until his arrival. The opera received its first performance on 5 May 1726 at the King's Theatre, London.

The story is based around Alexander the Great's journey to India, where he meets Poro, the king of India, who was the subject of another Handel opera of that name.