San Luis Potosí, commonly called SLP or simply San Luis, is the capital and the most populous city of the Mexican state of San Luis Potosí. It is the municipal seat of the surrounding municipality of San Luis Potosí. The city lies at an elevation of 1,864 metres. It has an estimated population of 824,229 in the city proper and a population of approximately 1,221,526 in its metropolitan area, formed with the neighbour city of Soledad de Graciano Sánchez and other surrounding municipalities, which makes the metropolitan area of Greater San Luis Potosí the eleventh largest in Mexico.
The city is in the west-central part of the state of San Luis Potosí, at 22.16°N, 100.98°W. The municipality has an area of 1,443.14 square kilometres. It is part of the macroregion of Bajío.
The city is named after Louis IX of France, who is the city's patron saint. Potosí was added in reference to the fabulously rich mines of Potosí, Bolivia, discovered some forty years before the city was founded, as the exploitation of silver and gold mines in Cerro de San Pedro, near San Luis, was the main reason for the founding of the city in 1592.