Nicolas Kiefer (born 5 July 1977 in Holzminden), is a German tennis player. His mother, Nicole, is French. He won a silver medal in men's doubles with partner Rainer Schüttler at the 2004 Summer Olympics in Athens.
Kiefer was taken notice of as an outstanding junior. He won the Junior Australian Open, US Open and was a finalist and semi-finalist at Wimbledon and the French Open finishing as the number 2 junior behind Zabaleta when he was 18.
On 10 January 2000, he reached his second quarterfinal at the Australian Open and afterwards was ranked World No. 4, his highest position to date.