Malesia is a biogeographical region straddling the Equator and the boundaries of the Indomalaya ecozone and Australasia ecozone, and also a phytogeographical floristic region in the Paleotropical Kingdom. It has been given different definitions. The World Geographical Scheme for Recording Plant Distributions split off Papuasia in its 2001 version.
Malesia was first identified as a floristic region that included the Malay Peninsula, the Malay Archipelago, New Guinea, and the Bismarck Archipelago, based on a shared tropical flora derived mostly from Asia but also with numerous elements of the Antarctic flora, including many species in the southern conifer families Podocarpaceae and Araucariaceae. The floristic region overlaps four distinct mammalian faunal regions.
The first edition of the World Geographical Scheme for Recording Plant Distributions (WGSRPD) used this definition, but in the second edition of 2001, New Guinea and the Bismarck Archipelago were removed from Malesia and were united with the Solomon Islands, previously placed in the WGSRPD's Southwestern Pacific region, being placed into a new region, Papuasia.