Betta splendens, also known as the Siamese Fighting Fish. A common pet fish best known for its flowing fins, vivid colouration, and its aggressive nature, often bullying fish its size or smaller and outright fighting other betta of its species to death.

While popular for its varied colourations and fin styles, wild betta are dull brown in colour and have shorter fins; the different colours and fin styles available to aquariums are the result of selective breeding.

They are native to Southeast Asia.