Arapaiminae is a subfamily of freshwater osteoglossiform (bony-tongued) fishes belonging to the family Osteoglossidae. It includes the South American arapaimas of the Amazon and Essequibo basins and the African arowana from the watersheds of the Sahelo-Sudanese region, Senegal, Gambia, and parts of Eastern Africa. This subfamily is sometimes raised to the rank of family, as Arapaimidae. A commonly used synonym is Heterotidinae, but according to the ICZN, Arapaiminae has priority.

Osteoglossidae is a family of large freshwater fish, which includes the arowanas and arapaima. They are commonly known as bonytongues. The family contains two extant subfamilies Arapaiminae and Osteoglossinae, with a total of five living genera. The extinct Phareodontinae are known from the Late Cretaceous and Paleogene.