I'll Have Another cut down the gallant Bodemeister late in the day to land the Kentucky Derby in front of a crowd of over 165,000 at Churchill Downs.

The strongly-fancied Bodemeister attempted to make virtually all in the 138th renewal of the 'Run for the Roses', setting the five fastest splits in Derby history, and still held a healthy lead entering the stretch.

Just as he looked like hanging on, the Doug O'Neill-trained I'll Have Another got to Bob Baffert's charge in the last 100 yards.

In winning, the Flower Alley colt became the first to win from stall 19, and was a maiden Derby victory for O'Neill - and a first on his first ride in the race for Mexican jockey Mario Guttierez.

Dullahan was third.

Aidan O'Brien's Daddy Long Legs showed up with the pace in the early stages but soon faded and eventually came home last, while favourite Union Rags was nearer last than first for a long way before staying on one-paced past beaten horses to finish seventh.

"He is an amazing horse," said Gutierrez, who moved to the United States less than a year ago after riding for six years in Canada.

"I told everybody before the first time I rode him, I knew he was the one."

I'll Have Another, who was bought last year by Canadian businessman J. Paul Reddam for just $35,000, emerged as a contender to win the annual Run for the Roses after winning last month's Santa Anita Derby in California.

But he was still considered an outsider in one of the most open Derbies in years, starting at odds of 15-1 and paying $32.60 for a $2 win bet.

"It is beyond belief," said winning trainer Doug O'Neill.

"Somebody asked me earlier in the week what it would be like to win the Kentucky Derby and I used Bubba Watson's quote when he won the Masters. I never dreamt this far. I never in a million years thought we could do it."

The connections wasted no time declaring their grand plans to tackle the Triple Crown. It has been 34 years since a horse has won the Kentucky Derby, Preakness Stakes and Belmont Stakes but Reddam said they would give it a go.

"Subconsciously, that was always the plan," said Reddam.

"We knew we had a good horse and we wanted to make sure he was fresh because the Triple Crown is a gamble.

"It looks like it paid off. We've only run three times this year so Preakness here we come."

Bodemeister lost no admirers after a bold front running display on the tight, dirt track.

He jumped straight into the lead from post position six and set a scorching pace on a humid day where the temperature soared.

Jockey Mike Smith kicked five lengths clear rounding the final turn but could not hold off the late sprint from I'll Have Another as he faded in the last furlong.

"He's a brilliant horse. That's the way we wanted him to run," said Bodemeister's trainer Bob Baffert, who is recovering from a heart attack he suffered while in Dubai in March.

"He ran his race. He was there and he just tired a little bit."

In keeping with tradition, the race was preceded by the singing of "My Old Kentucky Home" and the winner was draped in a garland of red roses as a huge crowd packed into the course, dressed in an array of outfits and sipping on mint julep drinks.