Ottone in villa (Otho at his villa, RV 729) is an opera in three acts by Antonio Vivaldi to an Italian libretto by Domenico Lalli (the pseudonym of Sebastiano Biancardi).

It was Vivaldi's first opera and premiered on 17 May 1713 at the Teatro delle Garzerie [it] in Vicenza.

[1] Lalli's pastoral drama is set in ancient Rome and was a condensed adaptation of Francesco Maria Piccioli's satirical libretto for Carlo Pallavicino's opera Messalina (1679).

Ostilio is in reality a woman, Tullia, who disguised herself because she's in love with Caio.

She plans to kill Cleonilla out of jealousy, but she first tries to dissuade her from her relation with Caio.