FINAL-ROUND LEADERBOARD (US unless stated)
-4 J Leonard, T Immelman (RSA), R Allenby (Aus)
-3 P Harrington (Ire), A Cejka (Ger) S Garcia (Spa), B Weekley
-2 T Pernice Jnr, S Verplank, G Coles (Aus)
Leonard was one of eight players who led in Tennessee
Justin Leonard holed a 19-foot birdie putt in a three-way play-off to clinch the Stanford St Jude Championship.
The American edged out Masters Champion Trevor Immelman and Australian Robert Allenby at the second extra hole.
The trio all finished on four under par and Leonard clinched victory after Allenby missed his 22-foot birdie putt and Immelman failed from 11 feet.
Leonard, who started the day three shots off the lead, closed with a 68, Allenby carded 65 and Immelman 69.
Overnight leader Tim Clark started the day two shots clear of the field but could not sustain his challenge in difficult conditions in Tennessee as he shot a 76 to finish on one over par for the tournament.
"It's been a great week and it's very nice to come out on top," said Leonard, who also won the tournament in 2005.
"I've kind of been back in the pack a little bit and was able to shoot a really solid round. I was able to hit some good shots in the play-off and make a nice putt there at 11."
When you win a golf tournament you have to really hold on to that feeling and take a lot of satisfaction.
Eight players held at least a share of the lead during the tournament and a birdie at the 15th resulted in Leonard taking a one-stroke advantage.
However, a wayward drive on the 17th led to a bogey that dropped him back into a three-way share of the lead with Allenby and Australian Gavin Coles.
A narrowly missed birdie on the par-four last resulted in him joining Allenby in the clubhouse on four under, while Coles hit a double-bogey to finish with 71.
Immelman, playing in the final pairing with Clark, booked his place in the play-off with a great finish - sinking birdies on the final three holes.
Victory was the perfect boost for 35-year-old Leonard ahead of this week's US Open and the Ryder Cup in September.
"I knew coming in here the best way for me to prepare is to gain confidence by playing well and do those little things in my practice session that I may need for next week," added Leonard.
"I would say in that department, I did a pretty good job. I feel like I've been playing some pretty good golf for the last eight, nine months but you can't always justify changes and good play with results.
"When you can, when you win a golf tournament, you have to really hold on to that feeling and take a lot of satisfaction."