Lydia Kingsmill Commander (October 18, 1869 – October 17, 1940) was a Canadian-born journalist, minister, and activist who worked mainly in the United States. Trained as a minister, she led a church in Wisconsin before moving to the Ruskin Colony. She then came to New York City, where she edited several magazines and was involved in the suffrage movement. Her book The American Idea (1907) argued that American families should have many more children in order to combat malign influences on the population.