San Dionisio Ocotlan is a town and municipality in Oaxaca in south-western Mexico. The municipality covers an area of 20.41 km². It is p…San Dionisio Ocotlan is a town and municipality in Oaxaca in south-western Mexico. The municipality covers an area of 20.41 km². It is part of the Ocotlán District in the south of the Valles Centrales Region.