Sefa is a town in Boyabat District, in Sinop Province, Türkiye. Sefa lies 1.3 km from the Ilgaz mountains. It has 802 inhabitants (2022). The nearest city is Boyabat, 3.3 km to the south. Among the landmarks around are Boyabat Castle (3.1 km) and Dodurga Dam (17.1 km).