Dumalinao is a coastal municipality in the province of Zamboanga del Sur.

The municipality has a land area of 117.64 square kilometers or 45.42 square miles which constitutes 2.62% of Zamboanga del Sur’s total area. Its population as determined by the 2020 Census was 32,928. This represented 3.13% of the total population of Zamboanga del Sur province, or 0.85% of the overall population of the Zamboanga Peninsula region. Based on these figures, the population density is computed at 280 inhabitants per square kilometer or 725 inhabitants per square mile.