Denis Gremelmayr (born August 16, 1981 in Heidelberg, Baden-Württemberg) is a German male tennis player. Gremelmayr turned pro in 2000 and reached #97 in August, 2006. He spent 2007 in the top 200 and finished the year at #119. His career high ranking is #59, achieved on May 5, 2008.
In 2008, Gremelmayr reached the second round of the Australian Open, losing in five sets to unseeded American Vince Spadea.
In April, he reached the semifinals of the Estoril Open, bowing out to then-ATP leader Roger Federer, in 3 sets.