The soldier was providing security in the Mirmandab region of Nahr-e Saraj, in the southern province of Helmand, when he was killed by an IED.
The soldier`s death brought to 386 the number of British troops killed since operations in Afghanistan began in October 2001. Of these, at least 341 were killed in combat. He is the 38th to die this year.
Britain has around 9,500 troops in Afghanistan, making it the second-largest contributor to the NATO-led International Security Assistance Force.
They are based in central Helmand, battling Taliban insurgents and training local security forces.
The body of the last British soldier killed in Afghanistan, Private Matthew Thornton, 28, was to be repatriated on Thursday. He was killed in an IED blast one week ago. (*)