Gianni di Calais is a melodramma semiserio, a "semi-serious" opera in three acts by Gaetano Donizetti (1828), from a libretto by Domenico Gilardoni, based on Jean de Paris by Louis-Charles Caigniez.
It was first performed on 2 August 1828 at the Teatro del Fondo, Naples.
The Duchess Adelina meets a masked woman with a child on the beach at night. The stranger turns out to be her friend, Princess Matilde, the king's daughter, fleeing to avoid having to marry the courtier Rogiero. During her flight she had fallen into the hands of pirates, but had been rescued by the ship-owner Gianni di Calais, who later became her husband. No one knows that the woman is the king's daughter except Gianni's faithful friend, Rustano. Gianni arrives with the sails of his ship showing images of his wife and son. He has been called to court by the king in order to search for his daughter. It is at this point that Gianni realizes the identity of his wife, and she appears at that moment. When the furious Rogiero sees her, he plans his revenge by kidnapping Gianni's and Matilde's son, but the boy is immediately rescued by Rustano. The king punishes Rogiero, and Gianni is accepted as Matlide's husband.