James Barry Munnik Hertzog, better known as Barry Hertzog, (1866-1942) was South Africa from 1924 to 1939.

In the general election of 1924, his National Party defeated the South African Party of Jan Smuts and became the government. In 1934, the National Party and the South African Party merged to form the United Party.

Hertzog was a republican who believed strongly in promoting the independence of the Union of South Africa from the British Empire. His government approved the Statute of Westminster in 1931, and in 1937 when King Edward VIII abdicated as King of the United Kingdom (and thus King of South Africa), Hertzog insisted the South African parliament "approve" this decision in a vote.

In 1939, the United Party caucus refused to accept Hertzog's stance of neutrality in World War II and deposed him in favour of Smuts.