The Cal 39 Mark II and Cal 39 Mark III are a series of American sailboats that were designed by C. William Lapworth as racer-cruisers to fit the International Offshore Rule and first built in 1978. The Cal 39 Mark II replaced the Cal 39 in the company product line and was in turn replaced by the derivative variant Cal 39 Mark III in 1983. The Mark III design was than replaced by the clean sheet Cal 39 (Hunt/O'Day) design in 1988.