Jacob [Jake] John Siemens (May 23, 1896 – July 12, 1963), was a Canadian farmer, co-operative leader, social entrepreneur, and adult educator. Born and raised a Mennonite near Altona, Manitoba, Siemens taught for 10 years before taking over the family farm in 1929. With the onset of the Great Depression he played a key role in the emergence of the dynamic co-operative movement in southern Manitoba. While he understood his work as an expression of Christian love, it ignited controversy within the Mennonite community. In his later years he left the Mennonite community and moved to Winnipeg, where he ran for office as a candidate for the New Democratic Party. On his death in 1963 he was buried at a Unitarian church.