Born in 1961, Northern Dancer was bred and owned by E. P. Taylor at Windfields Farm in Ontario, Canada. The cross that produced Northern Dancer came about by chance. His dam, Natalma, was sidelined from racing by a knee chip and was bred to Nearctic to help fill out the young stallion's first book. Natalma was the last mare Nearctic covered during the season. Northern Dancer was offered for CAN$25,000 at E. P. Taylor's annual pre-priced yearling sale at Windfields…There were no takers. Northern Dancer was originally consigned to Windfields' second string and trained by Peaches Fleming. After he won the Summer Stakes in his third start, he was taken over by Fleming's boss Horatio Luro, who trained the colt for the rest of his career. One of the smallest Kentucky Derby winners ever, Northern Dancer was also the youngest to date, winning the great race 25 days before his actual third birthday. A first-class racehorse up to 1¼ miles with the versatility to win on both dirt and turf, he was an even better stallion despite standing in Canada and then Maryland. A great sire of sires, he is the leading male-line progenitor of modern Thoroughbreds. A small, short-legged, muscular bay horse, Northern Dancer had powerful quarters and excellent balance and agility. Charles Hatton of the Daily Racing Form described Northern Dancer as having "a stride that looks two sizes too big for him but...perfectly controlled." While officially listed at 15.2 hands in his stallion advertisements, most horsemen personally familiar with Northern Dancer estimated his true height as between 15.0 and 15.1 hands. He had an exceptionally dominant personality with a high level of nervous energy and displayed much of the territorial behavior of a wild herd stallion, and he tended to pass his fiery disposition on to his progeny. The one person who seemed consistently able to charm him was Winifred Taylor, who had taken a particular liking to him when he was a foal and always brought him a bag of sugar cubes when she visited him; in turn, the horse would nicker a greeting whenever he saw her and would calm down for her even when inclined to be rambunctious with others.

Northern Dancer made 18 starts with a 14-2-2 record, earning $580,647 (including Canadian earnings).
In 1963 he won the Remsen Stakes (USA, 8FD), Summer Stakes (CAN, 8FT), Coronation Futurity (CAN, 9FD), and the Carleton Stakes (CAN, 7FD).
 In 1964 Northern Dancer won the Flamingo Stakes (USA, 9FD), Florida Derby (USA, 9FD), Blue Grass Stakes (USA, 9FD), Kentucky Derby (USA, 10FD, new track record 2:00), Preakness Stakes (USA, 9.5FD), and the Queen's Plate Stakes (CAN, 10FD). Northern Dancer was the first Canadian-bred to win the Kentucky Derby. He remains the only horse to win both the Kentucky Derby and the Queen's Plate, Canada's most important Classic race.
Honors

• National Museum of Racing Hall of Fame (inducted in 1976)

• Canadian Horse Racing Hall of Fame (inducted as part of the inaugural class in 1976)

• Ontario Sports Hall of Fame (inducted in 1998)

• Maryland State Athletic Hall of Fame (inducted in 2023)

• Canadian Horse of the Year (1964)

• Canadian champion 2-year-old colt (1963)

• American champion 3-year-old male (1964)

• Canadian champion 3-year-old male (1964)

• Named Canada's Athlete of the Year for 1964 by a vote of Canada's sports editors and journalists.

As a stallion

Northern Dancer entered stud at Windfields in 1965 and moved to the farm's Maryland division in December 1968. He was pensioned in 1987. After Windfields Farm closed its Maryland operation in 1988, it spent around $80,000 per year to maintain Northern Dancer as a pensioner until the stallion's death in 1990. His body was taken back to Canada and buried at his birthplace. According to Jockey Club records, Northern Dancer sired 411 winners (63.7%) and 147 stakes winners (22.8%) from 645 named foals. His progeny came in all shapes and sizes (though Charles O'Brien, son of the great Irish trainer Vincent O'Brien, described many of the ones trained at O'Brien's Ballydoyle yard as "piggy little things") but generally had excellent balance and acceleration and a share of his own tremendous will to win. The first North American-based stallion to sire 100 or more stakes winners, Northern Dancer proved an excellent sire of sires and had seven sons that also sired over 100 stakes winners. Northern Dancer is a Brilliant/Classic chef-de-race in the Roman-Miller dosage system. At the peak of Northern Dancer's stud career, “no guarantee” seasons to the stallion were selling for as much as $1 million and at the age of 20, Northern Dancer was the subject of a $40 million dollar offer from a European syndicate. The offer was turned down. Northern Dancer was rated #43 among the top 100 American racehorses of the 20th century by a panel of experts assembled by The Blood-Horse

Sire rankings

Per Great Thoroughbred Sires of the World (2006, Churchill, Reichard, and Rogers);

• Led the American general sire list in 1971; 4th in 1977; 5th in 1976; 6th in 1970 and 1978.

• Led the American broodmare sire list in 1991; 2nd in 1989; 3rd in 1992; 6th in 1990; 7th in 1984; 8th in 1983; 9th in 1988; 10th in 1980 and 1993.

• Led the English/Irish general sire list in 1970, 1970, 1983, and 1984.

• 3rd on the English/Irish general sire list in 1989; 4th in 1987; 6th in 1992.

• 2nd on the French general sire list in 1984.

• 4th on the French broodmare sire list in 1991.

• 3rd on the Japanese broodmare sire list in 1994; 9th in 1993.