Leishman made a blistering start as he gained six shots in his opening seven holes, including an eagle at the third, before finishing with a five-under-par 67 to sit on 19-under overall.
He was 6 under in his first 10 holes and ultimately fired a 7-under 65 as he cruised to a 26-under 262 total and a five-shot victory.
Leishman's winning form is good news for Australian fans ahead of his return home next month.
Woodland followed his course record-equalling second round 11-under with a battling 67, while 22-year-old Sharma dropped only one stroke for a gutsy 66 in hot and humid conditions.
Lee had a chance to win on the final day but a double bogey on the 16 hole undid her.
He charged through the first 10 holes in six-under with six birdies, including four straight from the second hole, and was so solid he was never threatened on the back nine. "I have had a few chances and didn't capitalise", Leishman said. "And the other holes, you know, irons into some of the tougher holes, I'm laying back".
Sorprende nino a Foo Fighters
Pero dejen eso de lado, porque el frontman más cool del momento se vio opacado por un niño de tan sólo 7 años. Luego de eso el niño se fue con su mamá a las gradas del recinto y muy feliz con su nueva guitarra en mano.
Leishman said: "A lot of good players at the top of the leaderboard. A par there would have gone a long way and I probably could have made more birdies after that".
Leishman moved away from the field with a birdie blitz on the front nine, where he made four consecutive gains from the second to the fifth before adding another at the ninth to make the turn on five under. It all would have looked a distant dream when the 34-year-old almost quit the game around the time of the 2015 Masters, when his wife Audrey was diagnosed with and nearly died from acute respiratory distress syndrome and toxic shock syndrome.
"The focus is just keep doing what I'm doing", Leishman said after his 62. Leishman stopped playing to take care of the family, but since then she has recovered since and Leishman won twice in 2017 and now once in 2018. We've been through that and that's not fun.
"Disappointing, not really happy with the way I finished". By the way, but if I wasn't to walk away the victor today, that's all right, too.
Two-time champion in 2015 and 2016, Justin Thomas, played the low round of the day at 8-under 64 to go up to T-5 alongside overnight co-leader Gary Woodland (71), Charles Howell III (67), Mexican Abraham Ancer (65) and former Open victor, Louis Oosthuizen (69). "I haven't been playing well for a while and to have a good tournament like this is really nice", said the 2014 Puerto Rico Open champion.