L'île de Tulipatan (The Island of Tulipatan) is an opéra bouffe (a form of operetta), in one act by Jacques Offenbach to an original French libretto by Henri Chivot and Alfred Duru.

It was first performed at the Théâtre des Bouffes Parisiens, Paris, on 30 September 1868. It was revived by the Compagnie Les Brigands at the Théâtre de l'Athénée as part of a double-bill with Croquefer in December 2012.

Octogène Romboïdal is the great steward of the supreme ruler of Tulipatan - Cacatois XXII. Romboïdal blames his wife Théodorine for their daughter Hermosa’s continual boyish behaviour. Hermosa enters firing off a rifle, and her father reproaches her for her neglect of needlework and the piano, but the tomboy is defended by her mother. Romboïdal mentions how gentle and gracious the prince Alexis son of Cacatois son is; Hermosa finds him charming and very pretty.

Next Cacatois and his suite enter to visit Romboïdal, followed by Alexis and his pages, the boy grieving the loss of his pet hummingbird, for which he is mocked by his father. As soon as the parents have left, Hermosa and Alexis burst into joyful song of their affections and Hermosa instructs the boy in how to declare love to her, but they are surprised by the return of Théodorine and Romboïdal just as Alexis says he will only marry Hermosa. Alexis demands that Romboïdal go with him to Cacatois to ask his consent.

Now Théodorine confesses to her daughter that she is a son – an interminable war at her birth made her mother fearful for her doing military service and therefore registered Hermosa as a girl. She worries how she is going to break the news to her husband whom she has fooled for 18 years.

Romboïdal returns, sends his wife on an errand then tells his daughter that the duke Cacatois was so determined to have a male heir after three daughters that his wife and Romboïdal telegraphed the ruler at war to say that he now had a son - and for 18 years Cacatois thinks he has a boy. Hermosa goes off, dancing, to the surprise of Romboïdal, who is more astonished when Alexis, who had over-heard some of this conversation, comes on in a dress.

Hermosa now re-enters dressed as a dashing guards officer. After a barcarolle Cacatois demands that Romboïdal and Théodorine consent for the daughter to wed his son Alexis. The confused couple eventually reveal their deception to their ruler, as the marriage procession enters. Cacatois simply declares that he will re-marry and try again for a son.