He succeeds Charlie Hughes, who left the position last month; Mr. Hughes had come out of retirement in October 2000 to manage the division in Irvine, Calif.
Mr. O'Sullivan had been manager of franchise and business development at Ford Motor Co.'s Lincoln Mercury division. The 50-year-old Detroit native has been with Ford since 1976 and held various key roles in marketing and sales.
Mr. O'Sullivan will now be responsible for all elements of Mazda's U.S. and Canadian operations, according to the company. Ford holds a controlling interest in Mazda's Japanese parent, Mazda Motor Corp.