Rhodeus is a genus of freshwater ray-finned fishes belonging to the family Acheilognathidae, the bitterlings.

Bitterlings inhabit slow-flowing or still waters, such as ponds, lakes, marshes, muddy and sandy pools, and river backwaters.

Bitterlings have a remarkable reproduction strategy where parents transfer responsibility for the care of their young to various species of freshwater mussels (Unionidae and Margaritiferidae).

The female extends her long ovipositor into the mantle cavity of the mussel and deposits her eggs between the gill filaments.

The male then ejects his sperm into the mussel's inhalent water current and fertilization takes place within the gills of the host.