Golf's next big thing began the day in a three-way share of the lead but produced four front-nine birdies, including three in a row from the par-five 5th, to lead by three at the turn.
He made a clutch up-and-down for par at the par-three 11th to extend his advantage to four shots before birdies at the 14th and 15th holes gave him a six-shot cushion.
The world number 14 added two more exclamation marks with birdies at the 17th and 18th holes to better the course record by two shots and complete a brilliant debut on Australian soil.
"That's definitely the best round I've ever played," Spieth said after the round.
"I didn't think that round was out there but the putts just kept going in."
The win sees the 21-year-old join golfing royalty on the Stonehaven Cup, with countrymen Jack Nicklaus, Arnold Palmer and Tom Watson among the previous winners of the prestigious trophy.
The next best round of the day belonged to Brett Holman who shot 67 before the 35km-plus winds arrived.
Veteran Rod Pampling (68) finished outright second at seven-under, one clear of Brett Rumford (70), with Greg Chalmers (71) a further shot back at minus-five.
Adam Scott (71) finished in solo fifth at four-under after starting the day one shot off the lead and with high hopes of winning his second Stonehaven Cup.
He looked set to make a charge after a brilliant birdie at the tough par-three 2nd but disaster was just around the corner.
The Queenslander missed a short par putt at the 4th to drop his first shot of the round before carving his drive into the right trees at the par-five 5th.
Scott was forced to take a penalty drop and compounded his problems when he found the left trees with his third shot.
He failed to find the green from the trees, eventually making double bogey to fall four shots behind then leaders Spieth and Chalmers.
Defending champion Rory McIlroy struggled to a one-over 72 to finish in a share of 15th spot.
After beginning the day six shots back the world number one missed short birdie putts at the 1st and 3rd holes before his title defence all-but ended at the par-five 5th.
After finding the fairway off the tee McIlroy tried to play a low draw into the wind but pulled his three-wood into the trees.
He clipped a branch with his fourth shot and failed to get up-and-down from the bunker to post a disastrous double-bogey and fall nine shots back.
A bogey at the 8th removed any hope of a Sunday charge.
Ironically, his first birdie of the day came at the par-four 9th, the hole he made a disastrous triple-bogey seven at on Saturday when he held a share of the lead.
He battled on around the back nine, cancelling out a bogey at 14 with a birdie at the 18th to card a one-over 72 and finish plus-two for the championship.