A British soldier from 4th Regiment Royal Artillery has died in hospital in Birmingham from injuries he received in an explosion in Afghanistan on 10 June.
The soldier, who has not yet been named, was on patrol in the Nahr-e Saraj North district of Helmand province when he was originally hurt.
The Ministry of Defence said the soldier's family has been told.
His death takes the total number of UK service personnel killed in Afghanistan since 2001 to 308.
Nineteen UK personnel have died this month, with 10 deaths in the past nine days.
Lt Col Chris Squier, the commanding officer for 4th Regiment Royal Artillery, said the soldier had been on a "reassurance patrol" with Combined Force Nahr-e Saraj North when he was injured.
"The soldier was on a joint patrol with the Afghan national army providing security to local villagers and protecting them from insurgent intimidation when his vehicle was struck by an explosion," he said.
The soldier was being treated at the Royal Centre for Defence Medicine (RCDM) Queen Elizabeth Hospital in Birmingham at the time of his death.
Lt Col Squier said: "Our thoughts are with his family at this exceptionally sad time."
The soldier's death came on the same day that thousands of people all over the UK took part in events marking their support for Armed Forces Day and just hours after Prime Minister David Cameron said he hoped UK troops would be out of Afghanistan within five years.