Onsernone is a municipality of the district of Locarno in the canton of Ticino in Switzerland.
Onsernone was created in 1995 when the municipalities of Comologno, Crana and Russo joined together to become Onsernone. On 10 April 2016, the former municipalities of Vergeletto, Gresso, Mosogno and Isorno merged into Onsernone.