Gréta Arn (born 13 April 1979) is a professional tennis player from Hungary, who previously represented Germany. Arn turned professional 1997.
In her career she won four ITF titles in singles and in doubles; she also won her first WTA title in Estoril, Portugal, on 6 May 2007, and her second in Auckland, New Zealand in 2011. Her career high on WTA rankings was No. 50, on 4 April 2011.
Arn was born in Budapest, Hungary. After playing for Germany with dual Hungarian citizenship for 9 years, she chose for the 2008 Fed Cup to compete for Hungary alongside Ágnes Szávay. She also chose to play for her nation of birth full time.