Dariusz Michalczewski (born 5 May 1968) is a Polish-German former professional boxer who competed from 1991 to 2005. He held multiple world championships in two weight classes, including the WBA, IBF, WBO and lineal light-heavyweight titles between 1994 and 2003, and the WBO junior-heavyweight title from 1994 to 1995.
Michalczewski came up through Poland's state-run sports program as a boy and had a successful amateur career. He achieved an amateur record of 139–11–2 (89 KO). Highlights of his amateur career include:
On 24 April 1988, while competing beyond the Iron Curtain in West Germany for the Polish national team, Michalczewski defected from the amateur team to stay in West Germany. Becoming a citizen of the now united Germany in 1991 and turning professional the same year, he was soon signed by Universum Box-Promotion, one of the leading boxing promoters in Europe. His aggressive style earned him the nickname "Tiger".