Diplahan, officially the Municipality of Diplahan (; ; ; ), is a municipality in the province of Zamboanga Sibugay, Philippines. According to the 2024 census, it has a population of 32,423 people.
Diplahan is politically subdivided into 22 barangays. Each barangay consists of puroks while some have sitios.
Based on the Köppen climate classification, Diplahan is considered a tropical rainforest climate (Köppen climate classification Af).