Sonogno és un municipi del cantó de Ticino (Suïssa), situat al districte de Locarno.
Sonogno is first mentioned in 1200 as Sornono. In 1417 it was mentioned as Senognio. During the Middle Ages, Sonogno was part of the Vicinanza of Verzasca and shared the fate of the valley. From 1395 to 1843, it formed a single community with Frasco.
It was part of the parish of Vogorno until 1519, when it formed a parish with Frasco. It formed an independent parish in 1734. The parish church of St. Maria Loreto, is first documented in 1519. It was rebuilt in 1854 and decorated with paintings by Cherubino Patà.
The local economy was based mostly on grazing. During the summer, the cattle grazed in the high alpine pastures, in the winter the cows were moved to their winter pastures in the Magadino. Due to limited jobs, many of the residents emigrated and after about 1850, many went overseas. Decedents of residents of Sonogno can be found in nearly 40 different countries. The more recent exodus to urban centers, combined with emigration have caused a steady decline of population since the mid-nineteenth century. The Museum of Verzasca was built in Sonogno in 1974. In 2005 the agricultural sector still offered 47% of jobs in the municipality.