Tommy Bonnesen (27 March 1873 – 14 March 1935) was a Danish mathematician, known for Bonnesen's inequality.
Bonnesen studied at the University of Copenhagen, where in 1902 he received his PhD with thesis Analytiske studier over ikke-euklidisk geometri (Analytic studies of non-Euclidean geometry).[1] He was the Professor for Descriptive Geometry at the Polytekniske Læreanstalt.
He did research on convex geometry and wrote a book on this subject with his student Werner Fenchel. Bonessen was an invited speaker at the ICM in 1924 in Toronto and in 1928 in Bologna.
With Harald Bohr he was for many years the co-editor-in-chief of the Matematisk Tidsskrift of the Danish Mathematical Society.
His younger daughter was the theatrical and cinematic star Beatrice Bonnesen (1906–1979). His elder daughter Merete Bonnesen (1901–1980) was a journalist employed by the newspaper Politiken.