Santo Domingo Petapa is a toun an municipality in Oaxaca in sooth-wastren Mexico. The municipality covers a aurie o 232.2 km², at an average altitude o 250 metre abuin sea level, an is pairt o the Juchitán Destrict o the Istmo de Tehuantepec region. As o 2005, the municipality haed a tot population o 7,583, 2,696 o wham spak indigenous leids.