San Mateo is a village in the municipality of Los Corrales de Buelna in the autonomous community of Cantabria, Spain. The runs through it. It is bordered to the north by, to the south-east by Los Corrales de Buelna and the west by Saja-Besaya Natural Park. In 2016, its population was 290.
It is the site of the Rebujas Rock festival.