The 18th BRDC International Trophy was a motor race, run to Formula One rules, held on 14 May 1966 at the Silverstone Circuit, England. The race was run over 35 laps of the Silverstone Grand Prix circuit, and was won by Australian Jack Brabham in the Brabham-Repco BT19. With no Race of Champions in 1966, the International Trophy formed the first major race of the European season, being run just a week before the start of the FIA World Championship in Monaco. The 1966 season was significant, as changes to the F1 formula had allowed an increase in engine capacity from 1.5L to 3L. This then was the first opportunity for many teams to test their new cars against top-line opposition.