Mazatlán, city and seaport, western Mexico, in Sinaloa State, on the Vigia Peninsula, overlooking Olas Altas Bay, an arm of the Pacific Ocean. A major tourist resort, it lies on the Pacific Railway and the western coast part of the Pan-American Highway, just south of the tropic of Cancer and near the entrance to the Gulf of California. Mazatlán possesses some light industry, and it is the largest Pacific port of Mexico. Hunting in the nearby mountains, fishing offshore, and bathing are the principal attractions of the area, and outstanding annual events are the pre-Lenten carnival and the international fishing tournament in the late fall. Picturesque islets in the bay, bird-filled mangrove swamps, an old Spanish fort, the city hall, an observatory, and one of the highest lighthouses in the world are also of interest. Founded in the early 19th century, the city quickly became industrially important. Population (2008 estimate) 4,804.