Senj is a town on the upper Adriatic coast in Croatia, in the foothills of the Mala Kapela and Velebit mountains.

The symbol of the town is the Nehaj Fortress (Croatian: Tvrdava Nehaj) which was completed in 1558. For a time this was the seat of the Uskoks (Italian: Uscocchi), who were Christian refugees from Ottoman Bosnia resettled here to protect the Habsburg borderlands. The Republic of Venice accused the Uskoks of piracy and declared war on them which led to their expulsion following a truce in 1617.

Senj is to be found in the Lika-Senj County of Croatia, the Roman Catholic Diocese of Gospic-Senj and the Roman Catholic Archdiocese of Rijeka.