Jan van Aswegen Steytler (born 1910, date of death unknown) was a liberal South African politician and the first leader of the Progressive Party (PP). He was born in Burgersdorp, in the then Cape Province now Eastern Cape Province.
Steytler was an Afrikaner. His father Louw Steytler was a veteran of the Second Boer War, who had helped found the National Party (NP). Louw Steytler became a Member of Parliament, as a supporter of J. B. M. Hertzog, who led the NP and then the United Party (UP) after the fusion of 1934. When the UP split in 1939, the Steytler family broke with Hertzog to remain in the UP as supporters of Jan Smuts. Louw Steytler died in 1945.
Jan Steytler went to England, in the 1930s, to study medicine at Guy's Hospital, London. As a student and later a member of staff, Steytler played first class Rugby Union for his hospital and was mentioned as a possible England player.
On the outbreak of the Second World War, Steytler returned to South Africa to become a member of the Medical Corps of the Union Defence Force. After the war he became a District Surgeon in the Cape town of Beaufort West, where he became active in politics.
Political career 
Steytler contested Beaufort West in the South African general election, 1948, as a UP candidate. Although he had no chance of election, in a strongly NP area, he was seen as a vigorous and attractive candidate. The following year he contested a by-election in another hopeless seat (De Aar-Colesberg), before being offered the UP candidacy in the safe UP seat of Queenstown.
Steytler was elected a member of Parliament in the South African general election, 1953. His comparatively liberal views were not welcomed by some UP leaders. However when boundary changes made Queenstown marginal, Steytler won the seat by a majoroity of 13 in the South African general election, 1958. As a result of his increased prominence Steytler became the leader of the UP in Cape Province and tried to persuade his party to take a more liberal direction on racial issues.
After failing to prevail within the UP leadership, Steytler became the leading figure in a group of progressives which eventually broke away to found a new party. Steytler resigned from the UP on 17 August 1959 and was named as the first leader of the Progressive Party, when it was founded on 13 November 1959.
The founders of the PP felt the UP was too conservative. Like all Progressive MPs with the sole exception of Helen Suzman, Steytler lost his seat in the South African parliament in the 1961 general election. Steytler remained party leader until he retired from the post in December 1970.
- The Times, edition of 12 November 1959 (a profile article setting out details of Steytler's background and political career)
- The Times, edition of 18 August 1959 (reignation) and edition of 14 November 1959 (founding and leadership of new party).