Balsa (Ochroma lagopus, synonym O. pyramidale) is a large, fast-growing tree to 30m tall, native from tropical South America north to southern Mexico. It is evergreen, or dry-season deciduous if the dry season is long, with large (30-50 cm) weakly palmately lobed leaves.

The timber is very soft and light with a coarse open grain. The density of balsa wood ranges from 100-200 kg per cubic metre (0.1-0.2 g/cubic cm), with a typical density of about 140 kg/cu.m (about one third the density of ordinary wood). This makes it a very popular material for model making and buoyancy materials (lifebelts, etc), and was famously used by Thor Heyerdahl in his raft Kon-Tiki.

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