The Municipality of Agdangan (Filipino: Bayan ng Agdangan) is a fifth class municipality in the province of Quezon, Philippines. According to the 2010 census, it has a population of 11,567.
In the late 18th century till early 19th Century Spanish Colonial era, the Municipality of Atimonan, Tayabas (now Quezon Province) was suffering from frequent attacks by Pirates and outlaws. A man from this place named Mariano Aguilar thought of moving to a safer place to live and dwell with his family. He asked a good friend and distant relative, Juan Salvador to help him find a nearby peaceful place to settle for good. Along with their immediate families, they walked through the forest south-west bound until they found a clean river. While traversing the riverside, they found a scenic body of water which was best described as ladder-like as the waters run over ladder-like steps. They initially named the place Hagdan-hagdan (ladder-like structure). This majestic scenery nowadays is a local tourist attraction that can be found in Barangay Dayap. As they moved further west, they found a huge, serene and attractive flat land area where they later established the town proper. In this land, they built houses for their families and divided the land area between their family members, relatives and friends. The population in this newly discovered area had increased dramatically and before the end of the 19th century, this place was officially called Agdangan (from the word hagdan-hagdan), a barrio of the nearby town Unisan, Tayabas.