Alfred Leon Foster (1904-1994) was an American mathematician. He was a professor at the University of California, Berkeley from 1934 until 1971. In 1932 he was an Invited Speaker at the ICM in Zürich. In 1934 he accepted a regular position at Berkeley. At that time Griffith Evans was Head of the Mathematics Department and was charged by President Sproul with building a first-class mathematics center, which he did. Alfred Foster and Charles Morrey (who became the first department chairman after Evans' retirement) were Evans' first two appointments. Except for subsequent sabbatical leaves, spent most notably in Freiburg and Tübingen, Foster served continuously at Berkeley until his retirement at the then-mandatory age of 67 in 1971.