Phil Mickelson said after Round 3 of The Open Championship that if he posted a final-round score in the 60s, he’d have a chance to win.

Mickelson did just that on Sunday, making birdies on four of his last six holes to shoot a final-round 66 and finish 3-under par, three shots clear of runner-up finisher Henrik Stenson.

“I’m playing some of the best golf in my career, and today was one of the best rounds I ever played,” Mickelson said after the round.

Click here to see what clubs in Mickelson’s bag at Muirfield.

Last week, Mickelson won the European Tour’s Aberdeen Asset Management Scottish Open, marking his first win on the continent. The 43-year-old can now claim a win at Europe’s most prestigious golf tournament, The Open Championship.

Mickelson entered the tournament as the No. 5-ranked golfer in the world, but his win at Muirfield won’t be measured by a boost in the world rankings — it’s a line on his career resume that cements him as one of the greatest golfers of all time.

Mickelson has now won three of golf’s four major championships — the Masters (three times), and the PGA and Open championships. The only major he is missing is the U.S. Open, where he’s finished in second place a record six times, including a second-place finish at this year’s tournament at Merion in June.

With the win, Mickelson joins modern day legends Seve Ballesteros, Peter Thompson and Byron Nelson with five major championships, as well as James Braid and John Henry Taylor, placing him in a tie for 14th for the most major championship wins of all time.

Final-round leader Lee Westwood, who started the round at 3-under, shot 75 to finish 1-over, in a three-way tie with Ian Poulter and Adam Scott for third place. Tiger Woods and Hunter Mahan, who started two shots behind Westwood, finished 2-over and 3-over, respectively.

Last year’s Open Championship winner, Ernie Els, finished the tournament in a tie for 26th at 8-over.