John Frederick Drummond (Jack) Jonas (circa 1881 – 2 July 1938) was an Australian politician. He represented the South Australian House of Assembly multi-member seat of Port Adelaide from 1927 to 1933 for the Labor Party. After leaving politics, he took over the District Hotel at Gumeracha and then was licensee of the Sevenhill Hotel at Sevenhill. He had shifted back to Adelaide and opened a business in Torrensville a few months before his sudden death in 1938.