Clifford Ambrose Truesdell III, was an American mathematician, natural philosopher, historian of mathematics, and polemicist.

Truesdell was born in Los Angeles, California. From 1961 until his retirement in 1989 he was professor of rational mechanics at Johns Hopkins University in Baltimore. He was the advisor of Walter Noll who contributed to foundational rational mechanics. The aim of rational mechanics is to construct a full mathematic model for treating mechanical phenomena. Truesdell was the founder and editor-in-chief of the journals Archive for Rational Mechanics and Analysis and Archive for the History of Exact Sciences, which were unusual in several ways. Following Truesdell's criticisms of awkward style in scientific writing , the journal accepted papers in English, French, German, or Latin.