Rattan, also spelled ratan, is the name for roughly 600 species of Old World climbing palms belonging to subfamily Calamoideae. The greatest diversity of rattan palm species and genera are in the closed-canopy old-growth tropical forests of Southeast Asia, though they can also be found in other parts of tropical Asia and Africa. Most rattan palms are ecologically considered lianas due to their climbing habits, unlike other palm species. A few species also have tree-like or shrub-like habits.

Calamoideae is a subfamily of flowering plant in the palm family found throughout Central America, South America, Africa, India, China, Southeast Asia and Australia. It is represented by 21 genera - containing nearly a quarter of all species in the palm family - including the largest genus, Calamus, the type genus of the group. Only four are found in the New World while the rest are Old World denizens, usually found in equatorial swampland or along tropical coastlines.