Private Stevie Richardson, from Tranent, East Lothian, took 4hrs 10mins to finish the 5km, cross-country Spartan obstacle race.
His German Shepherd dog called Sable, a neglected rescue dog who lost his front leg, could not resist joining him on part of the course at Winton House in Pencaitland, Scotland.
Pte Richardson, 26, was on a routine patrol with his Battalion 1 Scots in 2010 when he was injured by an improvised explosive device.
He teamed up with two other amputees, Private James Simpson, 28, and Private Jake Bartlett, 23, both from Leeds, who met at Headley Court rehabilitation centre, to complete the Spartan Race.
Wearing their prosthetic feet known as stubbies, the trio tackled obstacles and were among more than 2,500 competitors who took part.
There were 15ft rope climbs, slippery 7ft ramps, and sandbags had to be carried up steep hills dotted along the course which is designed to test mental and physical toughness.
Pte Richardson said: “The race was awesome, everything I thought it was going to be and more.
“I trained for seven months for this and nothing was going to stop us. It was very exciting to take part.”
Pte Richardson, who wears a long red beard, drew an ovation from the 3,000-strong crowd when he somersaulted through the fire jump.
“It was the only way I could think of to protect my beard from catching fire,” he said afterwards.
“I did actually trim it before the race and was hoping I’d get it wet before the fire. In the end, I just winged it and survived.”
Pte Bartlett, who lost one leg and badly damaged the other when he stepped on an IED in Afghanistan in 2009, said: “I raced in order to inspire other people and to prove to them that if amputees can do a Spartan race then they can do it, too.”
Pte Simpson said: “We took it slowly. My advice to people at home is to give it a go. Challenging yourself is important because it lets you find out what you’re about inside, what you’re like as a person.”
Dan Tuffnell, Director of Spartan Race UK, praised the trio for their “great determination” and “amazing achievement”.
“In view of what they have been through and what they have done for their country, I feel very moved and also thrilled to bits for them individually for their amazing achievement,” he said.
“They have shown great determination.”
These games come days after the Invictus Games, an international Paralympic-style event in which wounded soldiers took part in sports including wheelchair basketball, sitting volleyball and indoor rowing.