Arms and Explosive Search Dog, Buster is said to have saved "a thousand lives" in warzones around the world.
The springer spaniel has passed away at his handler's home in Lincolnshire, says the RAF.
Before retiring to live with Flight Sergeant Will Barrow, the 13-year-old dog had served in Afghanistan, Bosnia and Iraq - sniffing out bombs and booby traps before they could kill British service personnel.
He's said to have completed more tours than any other military dog.
As well as giving advanced warning of suicide bombers and hidden IEDs (improvised explosive devices), Buster also helped cheer up the troops, says his handler.
"Many's the time I'd find some of the soldiers on the cot beds with him, just chatting away. They felt they could confide in him and it wouldn't be going anywhere else."
He also made friends with local Afghans when he went out on patrol.
"We soon had a long train of children in tow - like a canine Pied Piper, Buster drew in his crowd and entertained them," says Flt Sgt Barrow.