Dariusz Tomasz Michalczewski is a Polish-German 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.

The World Boxing Organization (WBO) is an organization which sanctions professional boxing bouts. It is recognized by the International Boxing Hall of Fame (IBHOF) as one of the four major world championship groups, alongside the World Boxing Association (WBA), World Boxing Council (WBC), and International Boxing Federation (IBF). The WBO's headquarters are located in San Juan, Puerto Rico.