In a relentless performance at Dove Mountain, the 31-year-old Australian did not trail over the final 63 holes of the tournament and did not have a bogey on his card over the last 57 holes.
He took the lead with a 6-foot birdie on the first hole of a 36-hole title match and never gave Casey a chance. Ogilvy had a 3-up lead after the morning round, then shot 31 on the front nine to pull away.
A tournament that began with so much buzz over the return of Tiger Woods ended with a newfound appreciation for the match-play prowess of Ogilvy, who ran his career record to 18-3 in the format.
"The best thing I can say is I enjoy the format," Ogilvy said. "Generally, when you enjoy something, you do it well."
Ogilvy won his third World Golf Championship -- he will defend his title in two weeks at Doral in the CA Championship -- and has the most of any player besides Woods, who has won 15 of the elite events.
While Woods is a three-time winner of the Match Play Championship, Ogilvy ran his record in this tournament to 17-2. He lost in the championship match two years ago to Henrik Stenson, and lost in the first round last year to Justin Leonard.
Casey, who brought a 16-3-1 record in match play into the final, faced a 3-up deficit after the morning match and knew he had to play well to get back in the game. He birdied three of his next eight holes, and Ogilvy still stretched his lead to 5 up.
"I have no excuses right now," Casey said.
Ogilvy closed him out with a 6-foot birdie on the 15th hole. He won $1.4 million and moves up to No. 4 in the world ranking. He became the first player this year with multiple victories on the PGA Tour, having opened the year with a wire-to-wire win at Kapalua.
This was like a home game. Ogilvy now has won three times in the Tucson area over the past five years, starting with a victory in the old Tucson Open in 2005, before the Australian was eligible for the 64-man field at the Match Play Championship.
Since then, Ogilvy has won a U.S. Open, three WGCs and the winners-only Mercedes-Benz Championship.
Casey came into the final match having led 79 of the 80 holes he had played in his five previous 18-hole matches.
That amazing mark didn't last long.
Ogilvy made birdie from 6 feet on the first hole, and when Casey failed to match him from 5 feet, it was the first time the Englishman had trailed all week. From there, it only got worse.
Ogilvy had a putt to win on the next eight holes, converting three of them for a 4-up lead at the turn.
The final match is more marathon than sprint, though it was a bad omen for Casey. No one had come back from more than a two-hole deficit all week, and this was no exception.
The lone highlight for Casey came at the par-4 10th, when his 6-iron from 200 yards landed perfectly against the slope and rolled into the cup for an eagle. But on the next hole, Ogilvy regained control with a spectacular shot of his own: a chip-in for par from 60 feet.
In the third-place match, Stewart Cink beat Ross Fisher 1-up.