The pupil has beaten the master with Irish trainer Joseph O'Brien getting one-up on his famous father Aidan after Rekindling won the Melbourne Cup.

The youngest horse in the race as a three-year-old to northern hemisphere time, Rekindling was sent out by the youngest trainer for the most prolific owner in the race's history, Lloyd Williams.

Tuesday's win was Williams' sixth and jockey Corey Brown's second but a whole new experience for 24-year-old O'Brien who began training last year after a successful career as a jockey until weight got the better of him.

Williams, who had six horses in the Cup (3200m) including runner-up Johannes Vermeer who is trained by Aidan O'Brien, identified Joseph O'Brien as the trainer he wanted when he bought Rekindling to run in the race he is making his own.

Rekindling ($15) managed to avoid an early scrimmage and travelled well for Brown who said he was confident he would pick up Johannes Vermeer ($13) in the final 200 metres which he did to win by a long neck.

Max Dynamite ($20), runner-up in the 2015 Cup for another Irishman Willie Mullins, was another 2-1/2 lengths third.

"He is not a big horse, 420 kilos, but he is an easy horse to train," O'Brien said.

"Nick (Williams) suggested he would be an ideal horse for the Cup.

"We just keep him fresh and keep racing him.

"I'm almost speechless. He was brilliant and an unbelievable ride by Corey."

Brown, who won his first Cup on Shocking in 2009, said the race had not begun as he envisioned but panned out how he hoped.

"I was concerned in the first furlong because there was more early speed than I thought there would be," he said.

"There was a bit of confusion in front of me so I just let the horse relax and get into his rhythm.

"He was always travelling and I felt he was the winner a furlong out.

"I've won this race before but this time it feels a bit surreal.

"My manager identified this horse about six weeks ago and I rang Lloyd Williams with my resume.

"They got back to me within 24 hours so I've been looking forward to it knowing I was on a live chance."

Williams, who has won three of the past six Melbourne Cups with European imports Green Moon (2012), Almandin (2016) and Rekindling, said his latest winner would return to Europe for another race he covets, the Gold Cup at Royal Ascot which he won in 2016 with Order Of St George.

"He (Rekindling) will have a little while on the green grass at Macedon Lodge and then Joseph has to prepare him for the Gold Cup," Williams said.

"He is an extraordinary young trainer. He's close to being able to walk on water.

"It's great to see his career kicked off seriously here."

Marmelo, the well-supported $7 equal favourite for the Cup, finished ninth while Almandin, also $7, finished 12th under champion jockey Frankie Dettori who has yet to realise his Cup dream.

They were the only two runners under double figures with Wall Of Fire and Cox Plate runner-up Humidor, both at $11, finishing 16th and 19th respectively.