Spieth's 54-hole mark of 16-under 200 is the lowest in Masters history, beating the previous best of 201 that was achieved by Raymond Floyd and Tiger Woods.
The 21-year-old was impressive throughout his opening 36 holes, and continued that trend on Saturday, although he was forced to negotiate a few shaky moments.
Justin Rose is next best on 12-under, with Phil Mickelson one back on 11-under while Charley Hoffman sits on 10-under. Tiger Woods and Rory McIlroy head the remainder of the chasing pack on six-under.
Having made just one bogey in his first two rounds, Spieth notched up two more in his opening seven holes. But, birdies at the second, sixth and ninth saw Spieth take the turn in 35.
Birdies at the 12th and 13th allowed the Texan to take further control of proceedings, with Spieth at times looking untouchable. Back-to-back birdies at the 15th and 16th would quickly erase thoughts of a bogey at the 14th. However, it was at the 17th that Spieth faced his greatest challenge thus far.
Having sliced his tee shot left, he was forced to play out from behind a tree. A great iron shot followed to leave Spieth 20 yards from the green and seemingly out of trouble. An uncharacteristic error followed, with Spieth leaving his chip short and then three-putting for a double bogey.
With the world waiting for another mistake, Spieth found the gallery next to the 18th green, but he would produce a super chip shot and save par to calm some of the nerves that may have been developing.
A quality back nine from Rose saw him leap into second spot on 12-under. The Englishman birdied five of the last six holes to book his spot in the final pairing on Sunday.
Mickelson looked to be building momentum for a serious charge, but his progress was stymied by a bogey at the 17th. Regardless, 'Lefty' tied the low round of the day with a 67.
Woods is lurking on six-under, but the former world number one will feel that he could have posted a better score than his 68, having taken the turn in 32.
Three birdies on the trot from the second to the fourth saw Woods gain some early momentum, with a further shot picked up at the eighth. However, birdies at the the 13th and 15th were sandwiched either side of a bogey, with Woods dropping another shot on 18.
Perhaps the highlight of the 39-year-old's round was the birdie at the 13th after finding the trees off the tee. This would little matter though, as Woods played a great shot off the pine needles and found the green in three before holing a tricky downhill putt.
Woods is joined on six-under by McIlroy who was left to rue two late bogeys. An eagle three at the second saw the Ulsteman get off to the perfect start, with birdies at the eighth and ninth seeing McIlroy head to the back nine on four-under for the day.
Further birdies followed on the 13th and 15th, but bogeys at the 16th and 18th saw the world number one stumble into the clubhouse at six-under.