Seattle Slew (February 15, 1974 - May 7, 2002) was an American Thoroughbred race horse who won the Triple Crown in 1977--the tenth of twelve horses to accomplish the feat. He is the only horse to have won the Triple Crown while having been undefeated in any race previous. Honored as the 1977 Horse of the Year, he was also a champion at age two, three and four. In the Blood-Horse magazine List of the Top 100 U.S. Racehorses of the 20th Century Seattle Slew was ranked ninth.

Seattle Slew stood at stud at Spendthrift Farm in Lexington for seven years, before moving to Three Chimneys Farm in Midway in 1985. He was the leading sire of 1984, when his son Swale (who died later that year) won the Kentucky Derby and Belmont Stakes. His other progeny include the talented, ill-fated 1982 champion two-year-old filly, Landaluce, Slew o' Gold (winner of the 1983 Eclipse Award for Outstanding Three-Year-Old Male Horse and the 1984 Eclipse Award for Outstanding Older Male Horse), 1992 Horse of the Year A.P. Indy and the 2000 champion three-year-old filly Surfside. He is part of a unique three generation sequence of Belmont Stakes Winners: Seattle Slew (1977) - A.P. Indy (1992) - Rags to Riches (2004).  The primary conduit for Seattle Slew's continuation of his male line has been through A.P. Indy. A.P. Indy has done well at stud in Kentucky, siring (among others) the 2003 Horse of the Year, Mineshaft. One of Seattle Slew's most successful grandsons is the California champion Lava Man (sired by Slew City Slew). In 2006, Lava Man became the first horse to win the Santa Anita Handicap, Hollywood Gold Cup and Pacific Classic Stakes in the same year. Seattle Slew was also a leading broodmare sire, his daughters producing (among others) Cigar (leading North American money-earner of his day). Races in honor of his dam, My Charmer, include the My Charmer Handicap held at Florida's Calder Race Course annually and the My Charmer Stakes held at Kentucky's Turfway Park.  Rags to Riches, a granddaughter, won the 2007 Belmont Stakes - the third filly to win the race, after Ruthless in 1867 and Tanya in 1905. The victory earned jockey John Velazquez and trainer Todd Pletcher their first wins in any Triple Crown race. Rags To Riches was the 22nd filly to run in the Belmont. In 2002, ESPN telecast a "SportsCentury" on Seattle Slew.  In 2014, Seattle Slew's great-great grandson, California Chrome, won the Kentucky Derby  and the Preakness. California Chrome was the second Kentucky Derby winner in a row who was a sire-line descendant of Seattle Slew, following Orb in 2013. California Chrome's bid for the Triple Crown was defeated by another great-grandson of Seattle Slew, Tonalist, by leading sire Tapit. Tapit also sired the winners of the 2016 and 2017 Belmont Stakes, Creator and Tapwrit respectively.  25 years to the day after he won the Kentucky Derby, Seattle Slew died in his sleep at age 28. He was buried whole, the highest honor for a winning race horse, in the courtyard at Hill 'N' Dale Farm near Lexington, Kentucky, with his favorite blanket and a bag of peppermints which he liked to eat. Three Chimneys Farm erected a statue of Seattle Slew near the stallion barn in his honor. Since fellow Triple Crown winner and rival Affirmed had died the year before, he was the sole living Triple Crown winner. At the horse's death, there were no living Triple Crown winners for the first time since Sir Barton won the first Triple Crown in 1919. This phenomenon continued until American Pharoah's Triple Crown in 2015.

When did he retire?
25 years to the day after he won the Kentucky Derby, Seattle Slew died in his sleep at age 28.