Spieth, 23, bogied three holes in a shaky start as he threw away his advantage over Matt Kuchar at Royal Birkdale.
But then drama struck just as Spieth appeared to have steadied the ship with three pars to start the back nine.
He dropped out of the lead in extraordinary circumstances on the 13th in one of the most memorable moments in Open history.
After a wild drive into the rough, Spieth took a penalty for an unplayable lie, entitling him to go back in a straight line as far as he liked to find a favourable place to drop.
That happened to be the practice range between the 13th and 15th holes and specifically a truck belonging to one of the equipment manufacturers, from where Spieth could then get a free drop away from a temporary immovable obstruction.
Around 20 minutes after finding his ball, the 23-year-old eventually hit his third shot short of the green, chipped to seven feet and holed out for a remarkable bogey.
That gave Kuchar the outright lead, but that only lasted a matter of minutes as Spieth almost holed his tee shot on the par-three 14th and holed from three feet for birdie.
He then went on to make an eagle and two more birdies on his way to Open glory.
It sent fans wild on Twitter with one writing: “I have no idea how to describe what we are seeing from Jordan Spieth here. This is the stuff of legend. #BritishOpen.”
Another added “Epic resilience @JordanSpieth” while a fellow fan said “Ice in this boys veins… @JordanSpieth”.
A fellow impressed Spieth fan said: “This is the first time we’ve seen @JordanSpieth throw it in another gear at a major. Notice has been served. #TheOpen”
Another tweeted: “Don’t know if a golfer could ever be in #beastmode, but if so, @JordanSpieth is there! #britishopen.”
It was a view shared by thousands with one writing: “From a potentially legendary meltdown to: •Birdie •Eagle •Birdie •Birdie Amazing performance from Jordan Spieth at #TheOpen.”
Victory ensured Spieth joined Jack Nicklaus as the only other player to win three legs of the career Grand Slam before the age of 24.
