An airman taking part in a vehicle-mounted patrol in Afghanistan was killed following an explosion, the Ministry of Defence (MoD) said.
The airman, from 2 Squadron, Royal Air Force Regiment, part of the Kandahar Airfield Defence Force, died as a result of his injuries. His family has been told.
The blast happened on Wednesday night in an area north of Kandahar Airfield in Kandahar province.
Lieutenant Colonel David Wakefield, spokesman for Task Force Helmand, said: "It is my sad duty to inform you that an airman from 2 Squadron, Royal Air Force Regiment, part of the Kandahar Airfield Defence Regiment, was killed this evening as a result of an explosion.
"He was on a mobile patrol in an area about four kilometres north of Kandahar Airfield when the explosion happened.
"He died doing his duty and among his fellow airmen. His sacrifice will not be forgotten."
The death takes the number of British service personnel killed in the conflict to 264.
The MoD said 231 had been killed as a result of hostile action.
A further 33 died either as a result of illness, non-combat injuries or accidents, although some have yet to be assigned an official cause of death, a spokesman said.
The latest death was not linked to Operation Moshtarak - a joint UK, US and Afghan assault on insurgent strongholds.