Frederik Fetterlein (born 11 July 1970) is a retired tennis player from Denmark, who turned professional in 1989.
The right-hander Fetterlein represented his native country at the 1996 Summer Olympics in Atlanta, where he was defeated in the second round by Switzerland's Marc Rosset. Fetterlein reached his career-high ATP singles ranking of World No. 75 in October 1995. During his career, he defeated Thomas Muster and Stefan Edberg, amongst other top players.