Vincent O'Brien (9 April 1917 – 1 June 2009) was an Irish race horse trainer from Churchtown, County Cork, Ireland. In 2003 he was voted the greatest influence in horse racing history in a worldwide poll hosted by the Racing Post. In earlier Racing Post polls he was voted the best ever trainer of national hunt and of flat racehorses. He trained six horses to win the Epsom Derby, won three Grand Nationals in succession and trained the only British Triple Crown winner, Nijinsky, since the Second World War. He was twice British champion trainer in flat racing and also twice in national hunt racing; the only trainer in history to have been champion under both rules. Aidan O'Brien (no relation) took over the Ballydoyle stables after his retirement.