Gun Runner (foaled March 8, 2013) is a US Hall of Fame Thoroughbred racehorse who was the 2017 American Horse of the Year after winning four Grade I races at age four.

[3] His sire is Candy Ride, an Argentinian-bred horse who was undefeated in a six race career that included four Grade I wins in Argentina and the United States.

Although expectations for Candy Ride at stud were initially low, he proved himself a successful sire whose offspring include champion Shared Belief.

[4][5] Gun Runner is the first foal out of Quiet Giant, a multiple stakes winner from a distinguished female family that traces to Hall of Fame inductee Gallorette.

Following Evans' death in 2010, she finished her racing career under the ownership of his estate and was bought by Besilu Stables as a broodmare prospect at the Keeneland November sale in 2011 for $3 million.

[7][8] Quiet Giant was officially retired from racing and was bred to Candy Ride in 2012, resulting in the birth of Gun Runner at WinStar Farm on March 8, 2013.

"He was bright and inquisitive as a young horse, never much trouble and never sick or injured", according to Chris Baker, who was then the general manager of WinStar Farm.

Three Chimneys originally planned to re-sell Gun Runner at auction as a two-year-old but instead sold a half interest in the colt to Ron Winchell for an undisclosed price upon recommendation by his bloodstock advisor Dr. David Lambert and Equine Analysis Systems.

[9] Chris Baker, the chief operating officer of Three Chimneys, summarized Gun Runner's main assets: "Pedigree.

[1] On September 11, 2015, he made his career debut at Churchill Downs, winning a maiden special weight race over one mile by three-quarters of a length.

[1] On a muddy track, Gun Runner overcame some traffic problems to take the lead at the head of the stretch but was then overtaken and finished fourth.

[13] Gun Runner began his three-year-old campaign on February 20, 2016, in the Grade II Risen Star Stakes at the Fair Grounds Race Course.

"[14] On March 26, Gun Runner returned in the $1 million Louisiana Derby, also at the Fair Grounds, where he was the third betting choice at odds of just under 4–1.

[17] With his connections opting to pass the final two legs of the Triple Crown, Gun Runner returned to action on June 18 in the Matt Winn Stakes at Churchill Downs.

[19] He rebounded with a third-place finish in the Travers Stakes, though well behind the winner, Arrogate, who set a track record for 10 furlongs with a final time of 1:59.36.

"[20] On September 24, Gun Runner again faced off with Nyquist and Exaggerator in the $1.25 million Pennsylvania Derby at Parx Racing.

Meanwhile, Connect made his move along the rail and reached the lead in mid-stretch, then stood off Gun Runner's rally to win by half a length.

[21] After finishing second in the Breeders' Cup Dirt Mile, Gun Runner ended his three-year-old season on November 25 against a strong field of older horses in the Clark Handicap at Churchill Downs.

[1] Gun Runner was stabled over the winter at the Fair Grounds, which was quarantined in January after two horses tested positive for the neuropathogenic strain of the equine herpesvirus.

The connections of Gun Runner arranged to enter the horse in the inaugural running of the $12 million Pegasus World Cup on January 28 in what would have been his seasonal debut, but Gulfstream Park officials refused to allow him to travel to the track despite a negative blood test for the virus, as the horse had not been tested using a nasal swab.

Sent off as the 1–5 favorite in a field of six older horses, Gun Runner took the lead out of the gate and was never seriously challenged to win as he went 1+1⁄16 miles in 1:40.97, two-fifths of a second off the stakes record of 1:402⁄5.

[24] The win cemented Gun Runner's reputation for durability, reliability, and "consistent class" and encouraged his connections to run him in the $10 million Dubai World Cup.

[29] Highweighted at 124 pounds, Gun Runner drew post 3 in the Stephen Foster and was installed as the 4–5 morning line favorite.

On the second turn, 10–1 shot Stanford attempted to make a bid for the lead, but Gun Runner drew away to win by 7 lengths, a record margin of victory for the Stephen Foster.

After a good start, he settled into second place behind Cautious Giant, who had been entered as a "rabbit" for his stablemate War Story.

Entering the far turn, Geroux decided the pace was too slow and let Gun Runner assume control of the race.

[40] The race improved Gun Runner's rating to 127 in the Longines World's Best Racehorse Rankings August update, third place worldwide.

Trainer Todd Pletcher entered two horses, with Neolithic assigned to set a fast early pace in the hopes of tiring Gun Runner, while Rally Cry was intended to close from behind.

[42] His time of 1:47.43 was the fastest Woodward Stakes since the race was moved to Saratoga in 2006[43] and earned Gun Runner a Beyer Speed Figure of 115.

However, Geroux used Gun Runner's early speed to get racing room and moved quickly towards the rail, settling in second place just to the outside of Collected.