Reimund Dietzen sometimes written Raimund Dietzen (born 29 May 1959 in Trier, Rhineland-Palatinate) is a retired road and cyclo-cross cyclist from Germany, who was a professional rider from 1982 to 1990.

Dietzen was a successful amateur winning the German cyclo-cross championship in 1980 and 1981 as well as winning in road races. He turned professional with the Swiss team Puch in 1982. He won the cyclo-cross race the Grand Prix Jean Bausch-Pierre Kellner that year. The following year he joined a Spanish cycling team Teka with whom he would stay with for the rest of his career. In his first year with his new team he won the Volta a la Comunitat Valenciana. The following year he became the champion of Germany in the road race and cyclo-cross as well his first stage victory in the Vuelta a España. He won the stage to the Lagos de Covadonga which is a very steep climb and a prestigious stage to win. He would finish that year's edition of the Vuelta third overall. The following year he was again cyclo-cross champion as well as the winner of the Vuelta a Cantabria. In 1986 he was again German road champion and won a second stage in the 1986 Vuelta a España. In 1987 he wore the leader's jersey in the 1987 Vuelta a España for five days before losing it to Herrera and then finishing the race second overall to Luis Herrera of Colombia. Dietzen finished the 1988 Vuelta a España second overall, this time to Sean Kelly of Ireland. In the 1989 Vuelta a España, Dietzen won a stage but several days later he crashed. He had ridden into a tunnel which was not illuminated and crashed, suffering career-ending injuries. He was only 30 years of age when the following year he stopped as a professional after not recovering. Seventeen years later, the Supreme Court of Spain ordered the organisers of the Vuelta a España to pay damages to Dietzen. Dietzen obtained nearly all of his success in Spanish races with wins in Vuelta a La Rioja, Vuelta a Castilla y León and the Setmana Catalana de Ciclisme. From 2003, Dietzen was a directeur sportif with the now-defunct Team Gerolsteiner. He lives in Spain.