San Luis is a landlocked municipality in the coastal province of Pampanga.
The municipality has a land area of 56.83 square kilometers or 21.94 square miles which constitutes 2.84% of Pampanga's total area. Its population as determined by the 2020 Census was 58,551. This represented 2.40% of the total population of Pampanga province, or 0.47% of the overall population of the Central Luzon region. Based on these figures, the population density is computed at 1,030 inhabitants per square kilometer or 2,669 inhabitants per square mile.