San Mateo is an unincorporated community in Putnam County, Florida, United States, located just southeast of the city of Palatka. It is on the east shore of the St. Johns River between buoys 12 and 15; stretching from Buzzard Island to the entrance to Dunn's Creek.
It is located at , with an elevation of 72 feet (22 m). Businesses in the small town include the San Mateo Oasis, which is primarily a billiard and darts establishment that offers beer and wine for sale as well as water, soda and snacks and a hair salon that goes by the name, "Your Salon" which has been a fixture in the community for decades. The only restaurant is Chico's Mexican restaurant, adjacent to the Oasis.