The Mark Richards-skippered super-maxi, which had been pushed along for much of Thursday by strong northerly winds, crossed the finish line in Tasmania at about 0723 (2023 GMT) to break their own record by just under 20 minutes.
Their unofficial time was one day, 18 hours, 21 minutes and 17 seconds.
Wild Oats set the record of one day, 18 hours, 40 minutes and 10 seconds in 2005 when they not only took line honours for the 628-nautical mile blue water classic but also won the overall handicap title as well.
"Only just the race record and you know what 2005 was a great year but this year was so much better, this is a great result for the whole team," Richards told Australia's Channel 7. "We are absolutely stoked."
Last year's winners Ragamuffin Loyal - who pipped Wild Oats to the line by less than three minutes in 2011 - were about 50 nautical miles from the finish line in second place, though they will face a race jury later to determine whether they will be penalised for jumping the gun in Sydney on Wednesday.
Super-maxi Lahana were in third place, about 55 nautical miles behind Ragamuffin.
Wild Oats had been surfing at more than 24 knots down the east coast of Tasmania on Thursday and at one stage were more than 30 nautical miles ahead of her 2005 record pace before the westerly change.
They rounded Tasman Island off the south-eastern tip of the island state at about 0330 (1630 GMT) and had been projected to finish about 50 minutes outside their record.
A south-westerly wind, however, picked up just before they entered the Derwent River and propelled them to the finish where they were greeted by a large flotilla of boats escorting them to victory.
"It was a very tricky night," Richards added.
"The breeze died on us and then the southerly came through but it was very soft and very testing and we had to do a lot of sail changes and just worked ourselves into the ground and the guys did a great job but here we are and I'm very, very happy."
Richards said one of their daggerboards had hit an object early on Thursday, but it had not affected them too badly.
"We don't know what it was, it could have been a log or something," Richards said.
Wild Oats' victory moved them within one win of equalling the record of seven held by Morna/Kurrewa IV.
The start of this year's race on Wednesday had been shrouded in controversy with the exclusion of 2003 line honours winner Wild Thing for failing to provide necessary documentation for modifications to the boat.
Just two of the 76 boats to have started the race have so far been forced to withdraw, with Living Doll suffering a broken rudder while Primitive Cool damaged their mainsail.
Both were heading back to Eden on the New South Wales coast for repairs, race organisers said.