The , is a river in Saitama Prefecture, Japan. It is long and has a watershed of .
The river rises from Mount Ōmochi in Hannō, Saitama and flows to the Arakawa River at Kawagoe, Saitama. Before the flood control projects in the Edo Period, when the Ara River was diverted into its course, the Iruma River flowed on its own into Edo Bay.