Sagno is a former municipality in the district of Mendrisio in the canton of Ticino in Switzerland ; it is now part of the new municipality of Breggia. On 25 October 2009 the municipalities of Bruzella , Cabbio , Caneggio , Morbio Superiore , Muggio , Sagno merged into Breggia.

Sagno is first mentioned around 1296–99 as Sagnio.

Scattered finds from the Bronze Age suggest that the valley was settled prehistorically. During the Middle Ages it was part of the Pieve of Balerna. Together with Morbio Superiore it formed a vice-parish, which depended on the mother church at Balerna.