Lucrezia Borgia and Il pirata were two act operas, but Il pirata was based on a three-act melodrame.
Lucrezia Borgia is a melodramatic opera in a prologue and two acts by Gaetano Donizetti. 
Il pirata ("The Pirate") is an opera in two acts by Vincenzo Bellini to an Italian libretto by Felice Romani which was based on a three-act mlodrame from 1826, "Bertram, ou le Pirate" ("Bertram, or The Pirate") by Charles Nodier and "Raimonde" (actually Isidore Justin Sverin Taylor). 
