Sergeant Alexander Blackman, 39, will serve at least 10 years' imprisonment for murdering the Afghan national in Helmand province in 2011.
The married commando, known to friends and family as Al, said he was "very sorry" for his actions, which were filmed on the headcam of a comrade during the fateful patrol in "the most dangerous square mile in Afghanistan".
At the court martial in Bulford, Wiltshire, Blackman, a respected senior non-commissioned officer with 15 years' experience, was "dismissed with disgrace" from the Royal Marines.
Speaking after Blackman was led away to begin his sentence in a civilian prison, his solicitor Issy Hogg thanked the public for the support they have shown to him and his wife.
"Sgt Blackman and his wife are devastated by the life sentence imposed upon him together with the order that he serve a minimum of 10 years before he is eligible for parole," she said.
"Furthermore, he has been dismissed with disgrace from the Royal Marines, with whom he has served proudly for 15 years."
Miss Hogg added that Blackman, who until Thursday was known as Marine A when judges at the High Court in London ruled he should be named, intends to appeal.
Blackman was convicted last month following a two-week court martial in which his two co-accused, known only as Marines B and C, were acquitted of murder.
Blackman shot the Afghan, who had been seriously injured in an attack by an Apache helicopter, in the chest at close range before quoting a phrase from Shakespeare as the man died in front of him.
Blackman then turned to comrades and said: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."