The suborder Polyphaga contains the majority of beetles, with about 300,000 described species.

Among the commonly encountered polyphagans are the rove beetles (Staphylinoidea), scarabs and stag beetles (Scarabaeoidea), metallic wood-boring beetles (Buprestoidea), click beetles and fireflies (Elateroidea), as well as fungus beetles, grain beetles, ladybird beetles, darkling beetles, blister beetles, longhorn beetles, leaf beetles, and weevils (all Cucujiformia).

Aquatic lineages have evolved several times within Polyphaga. The largest groups are found within Hydrophiloidea and Byrrhoidea.