Hydaspes (also L’Idaspe fedele) is an opera by Francesco Mancini with a libretto by Giovanni Pietro Candi. It was first performed at the King's Theater in the Haymarket, London, on 23 March 1710. It was the second opera in England to be sung entirely in Italian, after Almahide, and was an early London success for the famous castrato Nicolò Grimaldi in the title role.