Which horse won the 1986 Kentucky Derby?

Ferdinand won the 1986 Kentucky Derby.

Ridden by Bill Shoemaker and trained by Charlie Whittingham, Ferdinand won the 112th Kentucky Derby at Churchill Downs. The victory was a major achievement for the late-maturing colt and helped establish him as one of the leading American racehorses of his era.

Ferdinand later won the 1987 Breeders’ Cup Classic, becoming one of the few horses to win both the Kentucky Derby and that championship race. His rivalry with Alysheba became a prominent feature of late-1980s American racing.

Alysheba won the 1987 Kentucky Derby, not the 1986 edition. Spend a Buck won in 1985, while Bold Venture won much earlier, in 1936, so all three names can appear in historical Derby lists without being the answer here.