Hydrophilus acuminatus, common name dark diving beetle, is a species of water scavenger beetles belonging to the family Hydrophilidae.

Hydrophilus acuminatus can reach a length of 33–42 millimetres (1.3–1.7 in).

The basic color of the body is dark brown or black.

These beetles have streamlined bodies and heads adapted for aquatic life, but they are not powerful swimmers.

This species can be found in Russian Far East, China, Japan and Korea.