Florence Reece (12 April 1900 – 3 August 1986) was an American social activist, poet, and folksong writer. She is best known for the song "Which Side Are You On?" which she originally wrote at the age of twelve while her father was out on strike with other coal miners, according to The Penguin Book of American Folk Song by Alan Lomax. In 1931, during the Harlan County strike by the United Mine Workers of America and the National Miners Union, in which her husband was an organizer, Reece updated her song to the version known today.