Louisa Jo Killen (né Louis Killen; 10 January 1934 – 9 August 2013) was an English folk singer from Gateshead, Tyneside. Killen also played English concertina and sang both unaccompanied and using this instrument to accompany herself while singing. Killen formed one of Britain's first folk clubs in 1958 in Newcastle upon Tyne and became a professional folk singer in 1961. In the 1970s Killen recalled: "When I started Folk Song and Ballad in Newcastle in 1958 there weren't twenty folk clubs in the whole country, and when I left for the States (in 1966) there were maybe three hundred." Recordings of Killen singing some Tyneside songs were included in The Iron Muse (Topic Records 12T86, 1963).
Killen emigrated to the United States in 1967 and worked with Pete Seeger before joining The Clancy Brothers. In 1971, the Clancy Brothers brought in the singer who had introduced the English concertina to the music mix, Lou Killen. They recorded two studio albums under the Audio Fidelity label: Save the Land and Show Me the Way. Their next, and final, album for Audio Fidelity was a live album, Live on St. Patrick's Day in 1973, recorded the previous year at the Bushnell Auditorium in Hartford, Connecticut. In the mid 1970s Killen left the Clancys.