Claude Lemaréchal was born in Paris in 1944. He has permanently worked for Inria (the French National Institute of Research for Computer Science and Control), where he is Director of Research; he led there several successive research teams (System Theory, Mathematical Programming, Numerical Optimization). He is renowned for his works in optimization, particularly in domains related with operations research and its links with nonlinear optimization (Dantzig Prize 1994). He has actively participated in the development of numerical methods in various branches of industry. Most significant results were obtained in geophysics (meteorology) and production management (electrical energy).