Aggressor (1955 – after 1971) was a British Thoroughbred race horse and sire. In a racing career which lasted from 1957 until July 1960 he ran twenty times and won eleven races. In his first three seasons he showed solid form, winning races including the Solario Stakes, the Coronation Stakes and the Cumberland Lodge Stakes. He reached his peak as a five-year-old in 1960 when he won the John Porter Stakes and the Hardwicke Stakes before recording his biggest success when defeating the outstanding filly Petite Etoile in the King George VI and Queen Elizabeth Stakes.