Guaymas (formally: Heroico Puerto Guaymas e Zaragoza) is a port city and a municipality in the Mexican state of Sonora. It stands on a small bay on the Gulf of California, near the mouth of the Río Yaqui, south of state capital Hermosillo and north of Ciudad Obregón. It serves as the administrative centre for the surrounding municipality of the same name, and for the neighborhood San Carlos Nuevo Guaymas, Sonora. Guaymas reported a population of 101,507 in the 2005 census, while its municipality had 134,153.