William David Ivy (27 August 1942–12 July 1969) was a British Grand Prix motorcycle road racer from Maidstone, Kent.
Ivy started racing motorbikes at Brands Hatch in 1959. He raced in the Grand Prix motorcycle racing championship towards the end of 1965, where he finished fourth in two 125 cc races and third in a 250 cc race. In 1966, he raced for the works Yamaha team, won the first race of the year at the Montjuich Circuit in Spain, and took three more wins—not enough, however, to beat Swiss rider Luigi Taveri, who beat Ivy to the title by six points.
In 1967, Ivy dominated the 125 cc championship: he won eight out of twelve races to claim the World Championship by 16 points over Phil Read . On top of this, he won two 250 cc races in France and Belgium.
In 1968, Ivy and his teammate Phil Read were in control of the 125 and 250 cc championships. Yamaha ordered them to win one title each, with Ivy scheduled to win the 250 cc championship and Read the 125 cc championship. After securing the 125 cc title, Read ignored Yamaha's orders to tie with Ivy on points. The tie break was decided on overall race times, and Read took the title. Ivy announced his retirement from motorcycle racing, stating he would race Formula Two cars during the next season.
On 22 June 1969 at Monza for the "Gran Premio della Lotteria", Bill Ivy had one of the incredible days of his life. He arrived for the first time to run the fast circuit in a car and after a few laps on Friday he formed the impression that Monza was a very dangerous track. Nevertheless he was prepared to start and presented his car in the pit lane at the beginning of the Saturday's session. It was reported that there was some confusion over paperwork, so Bill ran back to his van to collect the necessary docket.
When he returned, he was jostled by an official, resulting in an exchange of blows. Witnesses agreed that the first move was made by an Italian marshal, and the upshot was that Ivy refused to race, especially when he was forced to undergo a second medical during which he was informed that he was being examined to check whether or not he was under the influence of drugs! The test, of course, proved negative, and once tempers had cooled it looked as though Ivy would be permitted to practise, but he told his mechanics to take the car away and disappeared in search of some sunshine.
This was his last appearance into the Formula 2 continental circus. His double activity in motorcycle Grand Prix forced him to go to Sachsenring.
Despite showing some impressive results in Formula Two, he was enticed back to motorcycling by an offer from Jawa in 1969 to race their 350 cc motorcycle . The season started promising, as he took two second places behind Giacomo Agostini. However, during practice for the fifth race, in East Germany, Ivy was touring back to the paddock with his helmet resting on the tank when his motorcycle's engine seized. He was thrown from the bike, sustained massive head injuries, and died in hospital.