Betta fish are native to the Mekong Delta in southeast Asia, a wetland that extends from China to Vietnam. They were first kept as pet fish in Thailand and Malaysia. The common name for bettas is Siamese fighting fish, which comes from Siam, an old name for Thailand.
Bettas have been raised by people since at least the 19th century. They were caught in the local rice paddies and made to fight against each other for the amusement of on-lookers. Wild bettas live in deep, warm, slow-moving waters with dense vegetation. The colorful ornamental varieties available today are very different from the greenish wild-type fish. Selective breeding has produced the range of colors and fin types seen in aquariums today.