Machen is a surname often but not always of Welsh origin (derived from the town Machen). Notable people with the surname include:
Alwyn Machen (1901–60), British trade union leader
Arthur Machen (1863–1947), Welsh author and mystic, best known for his supernatural, fantasy and horror fiction
Bernie Machen (born 1944), American academic, President of the University of Utah (1999–2003) and of the University of Florida (from 2003)
Eddie Machen (1932–72), American boxer
Hervey Machen (1916–94), U.S. Representative from Maryland 1965–69
John Gresham Machen (1881–1937), American Presbyterian theologian
Ronald Machen (born before 1991), American lawyer, U..S. Attorney for the District of Columbia 2010–15
Thomas Machen (c. 1541–1614), English merchant who was three times mayor of Gloucester
William H. Machen (1832–1911), Dutch painter and teacher who relocated to America
Willis Benson Machen (1810–93), U.S. Senator from Kentucky 1872–73
