Spieth, bidding to become only the fourth golfer after Tiger Woods, Jack Nicklaus and Nick Faldo to successfully defend the Masters crown, did not drop a shot to par despite the difficult swirling wind on the opening day.
It left him a two shots clear of Ireland's Shane Lowry, who opened with five birdies in his first eight holes, and New Zealand's Danny Lee.
Rory McIlroy, who is bidding to complete his career grand slam of golf's majors, is four behind on a two-under after late dropped shots.
Spieth started strongly with birdies at the third, sixth, eighth, 10th and 13th before a crucial par-saving putt on the 16th kept his scorecard blemish free.
He closed in fine style with his sixth and final birdie of the day on the testing 18th.
Spieth, still only 22, has a remarkable record in the opening major of the season, finishing second on his debut in 2014 before donning the Green Jacket with a front running performance last year.
"It one of the better rounds I have ever shot," the young Texan told Sky Sports.
"Augusta is a place I feel comfortable. I feel you need imagination and you feel like with rich history here it excites you," he added.
Spieth has become the first golfer to lead the Masters for five rounds in a row and the first to begin his Masters career with nine consecutive rounds at par or better.
For much of the afternoon, it looked as if Jason Day, who recently usurped Spieth as world number one, might even surpass him at the top of the leader board.
Three birdies and an eagle took the Australian to the turn at five under and he maintained that position until the 15th where a missed par putt sparked an astonishing slump.
He triple-bogeyed the short 16th after finding the water and dropped a further shot on 17 on the way to a level-par 72.
"To be honest, I played great golf," he said. "If I went 41 on the front side and 31 on the backside I'd be just celebrating," he said.
Other highly favored contenders also struggled, with Rickie Fowler slumping to an eight-over 80.
The American never recovered from a double-bogey on the first hole, with an eight on the 13th wrecking any hopes of a recovery.
Australia's Adam Scott is also way off the pace after a disappointing four-over 76, his hopes of emulating his 2013 victory fading fast.
Spare a thought as well for the 'Big Easy' Ernie Els, who set an unwanted record high score at the Masters on the first hole. The South African, so close to winning at Augusta in the past, six-putted the green for a five-over nine, having officially been 'credited' with a 10 by the official scorer until it was later corrected.
A series of misses from three-feet and closer were hard to watch for the gallery, but the 46-year-old Els showed fighting quality to only drop three further shots in his round, despite his putting problems.
Els is highly unlikely to be around for the weekend, but 66-year-old golf legend Tom Watson has given himself a fighting chance of making the cut after a two-over 74.
The eight-time major champion is playing his final Masters and after a birdie at the third saw shots slip away on the seventh, 14th and 18th.
Northern Ireland's McIlroy, bidding for his fifth major, with the Masters the final one for his collection, looked dangerous on the back nine, eagling the par-five 13th and picking up a birdie on the 15th.
But bogeys on the 16th and 18th stalled his charge and he settled for a 70, still well-placed for a strong challenge over the next 54 holes.
A five-strong group of Europeans, including last year's runner-up Justin Rose, is tied for fourth on three-under 69.