Bautista notched up his 25th win in 34 races in Saturday afternoon's 20-lap contest, beating his nearest title rival Toprak Razgatlioglu by a margin of 1.195 seconds.
With only Sunday's two Jerez races to go, it means Bautista has an insurmountable 65-point lead with only 37 left on offer.
The 38-year-old Spaniard becomes Ducati's first repeat champion in WSBK since Troy Bayliss in 2006, and the first of the Italian marque's riders to successfully defend a title since Carl Fogarty in 1999.
"This season has been really good for us," commented Bautista post-race. "To win a title in always special, but to do it in your home country is even more so.
"I could not have imagined this kind of season at the beginning; I'm so happy."
Bautista went into the race needing only to score two points - equivalent to a 14th-place finish - to win the championship, while nothing less than victory would have been enough for Yamaha man Razgatlioglu.
While Bautista established himself in the lead from pole, Razgatlioglu made rapid progress from seventh on the grid to run second, and spent several laps circulating right on the tail of his rival.
But the Spaniard had the pace to pull away, and at one stage led as much as four seconds as he continued his record of winning at least one race in all 12 race weekends of the 2023 season.
Andrea Locatelli completed the podium in third on the second works Yamaha, while Jonathan Rea opened his final weekend as a Kawasaki with a solid run to fourth place.
Bautista established himself as the favourite to defend his 2022 crown early in the year with a treble win in the opening round at Phillip Island, repeating the feat at Assen, Barcelona and Misano.
It wasn't until the Imola round in mid-July that Bautista was defeated in a full-length race, with a crash for Bautista in the final race at the Italian track helping to ignite a brief comeback by Razgatlioglu.
But Razgatlioglu's chances of a second title took a major blow with a punctured tyre at Most, and by the time of the penultimate round at Portimao his faint hopes of challenging Bautista had all but been extinguished.
Sunday's two races will mark Razgatlioglu's last outings for Yamaha before he makes the switch to BMW, with Rea set to make his Kawasaki farewell as he takes over Razgatlioglu's seat in 2024.
