Siror (during the Habsburg Empire: Siraur) is a town in the municipality Primiero San Martino di Castrozza and was until 2015 a Northeast comune (municipality) in Trentino in the Trentino-Alto Adige. The village belonged to the Comunità di Primiero and bordered directly to the province of Belluno (Veneto). Part of the Lago di Calaita is located in the former municipality. Siror is located about 56 km east-northeast of Trent at the Parco Naturale Paneveggio - Pale di San Martino and the river Cismon at an altitude of 765 m.s.l.m. Patron saint of the town is the Apostle Andrew. On January 1, 2016, Siror concluded with the municipalities Fiera di Primiero, Tonadico and Transacqua together the new municipality Primiero San Martino di Castrozza. The municipality Siror had km² 2015 1277 inhabitants in an area of ​​75.03 on 31 December. To her the fractions Nolesca, Passo Rolle and San Martino di Castrozza belonged. Neighboring communities were Agordo (BL), Canal San Bovo, Imer, Mezzano, Predazzo, Tonadico and Transacqua.