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Tesco Boy (1963 – 25 October 1987) was a British thoroughbred racehorse and sire. While only moderately successful in racing, he became a major breeding sire in Japan in the 1970s and was on six occasions the leading sire in the country.

Tesco Boy was foaled in 1963. He was owned by Sir Jack Cohen, the founder of Tesco, who named the horse after the supermarket chain.^[2] As a race horse, Tesco Boy started in 11 races, winning five. His most notable result was a win in the 1966 Queen Anne Stakes, while also taking victories in lesser races, such as the Rose of York Stakes. He also placed in the Sussex Stakes, Queen Elizabeth II Stakes, and Champion Stakes the same year.^[2]

Tesco Boy was retired from racing in 1967, and was initially sent to stud in Ireland.^[4] At the end of 1967, he was exported to Japan to stand stud at the Hidaka Light Stallion Agricultural Cooperative's Monbestu Stud Farm in the Hokkaido region.^[5] In Japan, Tesco Boy saw massive success as a sire and became a major part of the Japanese horse racing bloodline. In six different years, Tesco Boy was the leading sire in Japan and his offspring would win nearly all of Japan's major races.^[6][7] Included among his most notable progeny are Kitano Kachidoki, Tosho Boy, Tesco Gaby, and Hagino Kamui O, all of whom won major races that would later be considered Grade 1 when grading was introduced to horse racing. Tosho Boy himself also became a successful sire after his racing career.^[8] As a broodmare sire, Tesco Boy was also highly successful, with his daughters producing such successful race horses as Ines Fujin, the 1990 Tōkyō Yūshun winner, Trot Thunder, the 1996 Yasuda Kinen and Mile Championship winner, and Nehai Caesar, the 1994 Autumn Tenno Sho winner.^[9] He is also the grandsire of Mr. C. B., who won the Japanese Triple Crown in 1983.

Another of Tesco Boy's grandsons, Sakura Bakushin O, became a successful sire in his own right, and Tesco Boy's bloodline continues in the 21st century mainly through descendants of Sakura Bakushin O. This includes Kitasan Black, of whom Sakura Bakushin O is the damsire of.

Tesco Boy died on 25 October 1987, aged 24.^[7][4]

c = colt, f = filly, g = gelding

bold = grade 1 stakes (or equivalent prior to grading)^[8]

Tesco Boy is also the broodmare sire of several grade-1 winning horses. These horses include the following:^[9]

• Bamboo Atlas, 1982 Tōkyō Yūshun
• Kushiro King, 1986 Spring Tenno Sho
• Gold City, 1986 Hanshin Sansai Stakes
• Ines Fujin, 1989 Asahi Hai Sansai Stakes and 1990 Tōkyō Yūshun
• Isono Roubles, 1991 Yushun Himba
• Trot Thunder, 1995 Mile Championship and 1996 Yasuda Kinen
• Nehai Caesar, 1994 Autumn Tenno Sho
• Daitaku Yamato, 2000 Sprinters Stakes
• Erimo Chic, 1997 Queen Elizabeth II Cup
• Narita Homare, 1998 Derby Grand Prix