Bougainvilliidae is a family of marine hydroids in the class Hydrozoa.

[2] There are sixteen accepted genera and about ninety-three species.

When colonial, the hydranths or hydroid polyps are either linked by stolons or are branched.

The gonophores are free-living medusae or are fixed sporosacs.

The medusae are bell-shaped with a circular mouth and branched oral tentacles inserted above the rim of the mouth, ending in clusters of nematocysts.