Betta /ˈbɛtə/ is a large genus of small, active, often colorful, freshwater ray-finned fishes, in the gourami family (Osphronemidae).

This accounts for their ability to thrive in low-oxygen water conditions that would kill most other fish, such as rice paddies, slow-moving streams, drainage ditches, and large puddles.

[2] The bettas exhibit two kinds of spawning behaviour: some build bubble nests, such as B. splendens, while others are mouthbrooders, such as B. picta.

The mouthbrooding species are sometimes called "pseudo bettas", and are sometimes speculated to have evolved from the nest-builders in an adaptation to their fast-moving stream habitats.

[3] A phylogenetic study published in 2004 concluded tentatively that bubble-nesting was the ancestral condition in Betta, and that mouthbrooding has evolved on more than one occasion in the history of the genus.

[11] This likely refers to the extirpated Singaporean population of B. tomi, which continues to exist in the wild in Indonesia and Malaysia, as well as in captivity; the Red List classifies it as Vulnerable.