Ion radiation is a form of radiation associated with ions.

The detonation of a Federation photon torpedo produced ion radiation, which could be hazardous to unshielded starships at close ranges. When the USS Enterprise-D disrupted a soliton wave using photon torpedoes in 2368, parts of the ship were flooded with ion radiation due to gaps in its damaged shield grid. (TNG: "New Ground")

Ion radiation was one of the sources of interference accounted for by the USS Voyager crew during their hunt for the missile Dreadnought in 2372. (VOY: "Dreadnought")

It is unclear how or if this relates to ionizing radiation.