[4] The origin of the name of Gasan came from the term Gasang or Gasang-Gasang, a type of coral once abundant around the town's shoreline.

Legend has it that when the Spaniards discovered the town, they found an old woman near the banks of today's Matandang Gasan River.

In 1945, the combined United States and Allied Philippine Commonwealth forces landed in Gasan, Marinduque.

[6][7] The municipality is bounded by the provincial capital, Boac, to the north and east, by Buenavista to the southeast and by the Sibuyan Sea to the south and west.

The Tres Reyes Islands off the coast of Marinduque are under the jurisdiction of Gasan, part of the municipality's Barangay Pinggan.

", the municipal government promoted individual barangays' products and landmarks in a bid to showcase Gasan as a tourist destination.