Gajac (Italian: Porto Castello) is a village on the Adriatic Sea on the island of Pag, in Lika-Senj County. Administratively, it is part of the town of Novalja. There is a small permanent population and a seasonal tourist population from in and out of Croatia who lease or buy condos. According to the 2021 census, it had a population of 86. Nearby locations include Zrće Beach, a well-known partygoers destination, and Kolansko blato, an ornithological reserve.