Vergeletto is a former municipality in the district of Locarno in the canton of Ticino in Switzerland . On 10 April 2016 the former municipalities of Vergeletto, Gresso , Mosogno and Isorno merged into the municipality of Onsernone .

In the Middle Ages Vergeletto belonged to the Onsernone Vicinanza and to the squadra of Russo. In 1803 the municipality of Vergeletto also included the municipality of Gresso, both municipalities separated into independent municipalities in 1882. Vergeletto was part of the parish of Russo until 1757, when it became an autonomous parish.

Vergeletto had an area, as of 1997, of 40.79 square kilometers (15.75 sq mi).