Frithjof Kleen (born 25 June 1983 in Berlin) is a German sailor, who specialized in two-person keelboat (Star) class.

[1][2] He represented Germany, along with his partner Robert Stanjek in the Star class at the 2012 Summer Olympics, and also captured a silver medal at the 2011 ISAF Sailing World Championships in Perth, Australia.

[3] Kleen has also been training throughout most of his sporting career for the North German Sailing Regatta (German: Norddeutscher Regatta Verein) in Hamburg under his personal coach Alan Smith.

[1][4] Kleen qualified as a crew member for the German squad in the Star class at the 2012 Summer Olympics in London by placing second and receiving a berth from the ISAF World Championships in Perth, Western Australia.

[3][5] Teaming with his partner Robert Stanjek in the opening series, the German duo recorded a net score of 70 points throughout the entire race, but came up short for the medal podium with a satisfying sixth position against a fleet of sixteen boats.