Sibunag is one of the two new municipalities created in the province of Guimaras through RA 7896. Such creation was validated with COMELEC Resolution en banc after the plebiscite conducted during the May 1995 election.
Situated Southeast of Guimaras Island facing Negros and is separated from that island by Guimaras Strait. It is composed of fourteen (14) barangays where the twelve (12) barangays were from the mother Municipality of Jordan and two (2) barangays were from Nueva Valencia. Sabang, San Isidro, Sebaste, Alegria, and Bubog are the coastal barangays while Maabay, Dasal, Ayangan, Ravina, Millan, Tanglad, Oracon and Concordia are the inland barangays and Inampulogan, which is an island barangay. It has a total population of 17,773 scattered among 14 barangays and a total land area approximately 147.40 square kilometer occupying 21% of the total land area of the whole province.
Even before it was created as separate Local Government Unit, Sibunag is named after its main river, abounds with spellbinding folktales and legends.
The tragic story of Guima and Aras (popularized by Guimaras writer, Romeo G. Garganera) happened in the shores of Sibunag as the ill-fated lovers desperately crossed the stormy sea to Baglas, now Negros, to escape the wrath of an angry father.
Legend also says that Sibunag, son of a deity and a mortal was stolen when only a baby. He was cared for and raised by a fairy. His numerous and amazing adventures and romance found niche in the hearts of folklore writers.
Sibunag river remains even today, not only the main source of gravel and sand supply of the province but also an important waterway from the mainland Guimaras to the island waters where the longest river in Guimaras could be seen with its tributaries originate from the springs of the three mountains of Dinalman, Bontoc and Tigbi, strategically located in Barangay Millan. By mouth of Sibunag River are wide areas of fishponds. Along its shorelines to Alegria and San Isidro are sources of bangus fry, bulgans, talakitok, mayamaya, kanlay, crustaceans especially the kamuntaha, lobsters, prawns and seashells.