Big Blue Kitten (foaled May 1, 2008) is an American Thoroughbred racehorse who specialises in turf races. Unraced as a juvenile, he finished third on his debut in 2011 and then went on a five race winning streak, culminating in a victory in the Grade II National Museum of Racing Hall of Fame Stakes. After winning one minor race as a four-year-old he emerged as a top-class turf performer in 2013 when his wins included the United Nations Stakes and the Sword Dancer Invitational Stakes. His only win of consequence in 2014 came in the Lure Stakes but he returned to his best as a seven-year-old in 2015 winning the Fort Marcy Handicap, a second United Nations Stakes and the Joe Hirsch Turf Classic Invitational Stakes. Apart from his victories he finished second in the Arlington Million and third in the Breeders' Cup Turf. His performances earned him the title of American Champion Male Turf Horse for 2015.

Big Blue Kitten is a bay horse bred and owned by Kenneth and Sarah Ramsey. He was sired by the Ramsey stallion Kitten's Joy the U.S. Champion Male Turf Horse of 2004. His dam, Spent Gold made no impact on the track, failing to win in three races as a two-year-old in 1999.^[2] She was a granddaughter of Mystical Mood who won the Schuylerville Stakes and produced the Citation Handicap winner Fair Judgment.^[3]

The Ramseys sent their horse into training with Chad Brown. Although Big Blue Kitten is an entire male horse he is officially described as a ridgling, as he has an undescended testicle. The "Big Blue" part of his name is a reference to the sports teams of the University of Kentucky, Ken Ramsey's alma mater.^[4]

Big Blue Kitten began his racing career by finishing third in a maiden race at Gulfstream Park on February 21 and then opened his winning account in a similar event over nine furlongs at the same track on 20 March. He went on to win a minor turf race at Keeneland in April, and gained further successes at Belmont Park in May and July to take his winning run to four. On August 12 at Saratoga Race Course, Big Blue Kitten was stepped up in class for Grade II National Museum of Racing Hall of Fame Stakes and started second favorite in a seven-runner field. Ridden by John Velazquez he tracked the leaders before moving up on the rail, taking the lead in the straight and winning by one and a quarter lengths from Perregaux.^[5] Commenting on the horse's successful step up in class, Ramsey said "We’ve offered this horse for a claiming price three times and no one claimed him. No more claimers!" ^[6] The colt was then off the course for four months before finishing third in a minor race at Gulfstream in December.

On his 2012 debut, Big Blue Kitten was moved up to Grade I level for the Gulfstream Park Handicap and finished third behind Get Stormy and Hollinger. In the Ben Ali Stakes at Keeneland in April he finished a distant second to the five-year-old gelding Wise Dan. He was then sent to England to contest the Prince of Wales's Stakes at Royal Ascot in June. Starting a 50/1 outsider, he briefly took the lead a quarter of a mile out before fading in the final furlong to finish tenth of the eleven runners behind So You Think.^[7] On his only other start of the year he won a minor race at Gulfstream in December.

In 2013, Big Blue Kitten began his campaign by finishing third to Mucho Mas Macho in the Fort Lauderdale Stakes and then won minor events at Gulfstream in March and Churchill Downs in May. In June he moved to Monmouth Park where he was partnered for the first time by Joe Bravo, who became his regular jockey. He finished second to Boisterous in the Monmouth Stakes and then contested the Grade I United Nations Stakes over one mile three furlongs on 6 July. The Breeders' Cup Turf winner Little Mike started favorite, with Big Blue Kitten second choice in the betting at odds of 2.5/1 and the 2011 winner Teaks North on 7.6/1. After being restrained by Bravo in the early stages he made rapid progress on the rail in the straight, took the lead in the closing stages and won by one and a quarter lengths from Teaks North.^[8] Chad Brown described Bravo's ride as "one for his highlight reel" and added that "this horse will run as far as you want".^[9]

On August 17 Big Blue Kitten was one of twelve horses to contest the Grade I Sword Dancer Invitational Stakes over one and a half miles at Saratoga. His opponents included Boisterous, Twilight Eclipse (Pan American Stakes), Stormy Lord (Connaught Cup), Al Khali (Bowling Green Handicap) and Optimizer (Kent Stakes). After racing towards the rear of the field he began to make progress on the inside but failed to obtain a clear run in the straight. Bravo switched him to the outside in the final furlong and Big Blue Kitten produced a strong late run to take the lead and won "readily" by a length from Twilight Eclipse.^[10] Brown said that he had been "super confident" before the race while Bravo commented "the happiest I was was turning for home. I'm looking at each rider and they're riding their horses, and I hadn't even asked the Kitten yet".^[11]

Big Blue Kitten started odds-on favorite for the Joe Hirsch Turf Classic Invitational Stakes at Belmont Park on September 28 but in a closely contested finish he was beaten a nose into second by Little Mike. On his final appearance of the year he finished eighth behind Magician in the Breeders' Cup Turf at Santa Anita Park on November 2.

Big Blue Kitten missed the first half of the 2014 season, making his debut in the Listed Lure Stakes at Saratoga on 12 August. Starting the 1.7/1 favorite he came from well off the pace to take the lead in the last 50 yards and won by three quarters of a length from Bio Pro.^[12] Brown was delighted with the performance, saying "What a great horse. I wasn't quite sure if I had him fit enough off the layoff. I told Joe if he won, it'd be terrific, but as long as he finished well we had some big plans for this horse later in the year. Lo' and behold, he got through anyway on heart".^[13]

Later that month he finished second at Monmouth and in September he finished fourth to Main Sequence in the Joe Hirsch Turf Classic. In October he was sent to Toronto for the Canadian International Stakes in which he finished second to the British colt Hillstar. On his final start of the year he started favorite for the Red Smith Handicap in November but was beaten into second place by Dynamic Sky.

Big Blue Kitten began his fifth season in the Grade III Fort Marcy Handicap at Belmont on May 2. Ridden as usual by Bravo, he started favorite in an eight-runner field and won by two and a quarter lengths from Howe Great with the Travers Stakes winner V E Day in sixth.^[14] Bravo explained his tactics by saying "if you just point him at horses, he'll run them down. And ever since the first time I rode, that's all I've done—point him at horses."^[15] In the Grade I Manhattan Handicap at the same track in June, he struggled to obtain a clear run in the straight before finishing second, two and three quarter lengths behind his stable companion Slumber. Big Blue Kitten and Slumber met again in the United Nations Stakes on Monmouth on July 5, where the other contenders included Main Sequence, Twilight Eclipse and the San Luis Rey Handicap winner Ashleyluvssugar. After being restrained by Bravo as usual, he produced a strong late run to take the lead a furlong out and won the race for the second time, beating Slumber by a length and a half.^[16] Joe Bravo described the winner as "just like an old glass of wine, he keeps getting better with age".^[17]

In August Big Blue Kitten was sent to Chicago to contest the Arlington Million and started 3/1 joint favorite alongside Slumber and the Stars and Stripes Stakes winner The Pizza Man. He was held up for his customary late charge but failed by a neck to catch The Pizza Man. On September 26 Big Blue Kitten made his third attempt to win the Joe Hirsch Turf Classic Stakes at Belmont. He started second favorite behind the Bowling Green Handicap winner Red Rifle in a field which also included Slumber and Twilight Eclipse. He was held up as usual before overtaking the pace-setter Shining Copper in the last quarter mile. He opened up a clear advantage and held off the late challenge of Slumber to win by three quarters of a length.^[18] The winning time of 2:23.9 was a new turf track record and the fastest mile and a half ever run at Belmont, beating Secretariat's 2:24.0 on dirt in the 1973 Belmont Stakes.^[19]

Big Blue Kitten ended his season in the Breeders' Cup Turf at Keeneland on October 31. He proved the best of the North American horses as he finished a close third to the European challengers Found and Golden Horn.

In the Eclipse Awards for 2015, Big Blue Kitten was named American Champion Male Turf Horse, taking 134 of the 261 votes to win from Golden Horn and The Pizza Man.^[4]

Big Blue Kitten went winless in three starts as an eight year old. He began his sixth year of racing in the Woodford Reserve Turf Classic, finishing fifth behind Tourist (who would go on to win the Breeders' Cup Turf Mile), Slumber, World Approval, and winner Divisidero. He then ran in the Manhattan Stakes, finishing sixth. After running last in the Northern Dancer Turf Stakes, the decision was made to retire him. Big Blue Kitten retired to Calumet Farm. His 2017 fee was set at $15,000.^{[citation needed]}

• Big Blue Kitten is inbred 4 × 4 to Roberto, meaning that this stallion appears twice in the fourth generation of his pedigree.