Freddy Delbaen (born 21 November 1946 in Duffel, Belgium) is a Belgian-Swiss mathematician.

[1] He studied mathematics at the Free University of Brussels and received his doctorate there in 1971 under the supervision of Lucien Waelbroeck.

In 1995, Delbaen became a full professor at the ETH Zurich, remaining there until his retirement in 2008.

[7] Together with Walter Schachermayer, he proved a general form of the fundamental theorem of asset pricing for (locally) bounded semimartingales, replacing the condition of "no arbitrage" with the term no free lunch with vanishing risk (NFLVR).

[9] In a joint paper with P. Artzner, J. M. Eber and D. Heath, he introduced the concept of (coherent) risk measure on a finite probability space.