Joseph Siffert (July 7, 1936 – October 24, 1971) was a Swiss racing driver.
Affectionately known as "Seppi" to his family and close friends, Siffert was born in Fribourg, Switzerland, the son of a dairy owner. He initially made his name in racing on two wheels, powering his way to the Swiss 350 cc motorcycle championship in 1959, before switching to four wheels with a Formula Junior Stanguellini. Siffert graduated to Formula One as a privateer in 1962, with a four-cylinder Lotus-Climax. He later moved to Swiss team Scuderia Filipinetti, and in 1964 joined Rob Walker's private British Rob Walker Racing Team. Early successes included victories in the non-Championship 1964 and 1965 Mediterranean Grands Prix, both times beating Jim Clark by a very narrow margin. Siffert was married twice and to his second wife Simone during the height of his career in the late 1960s and at the time of his death in 1971. They had two children together, Véronique and Philippe.