Gréta Arn (born 13 April 1979) is a Hungarian former professional tennis player of Danube Swabian German descent.

After playing for Germany with dual Hungarian citizenship for nine years, she chose for the 2008 Fed Cup to compete for Hungary alongside Ágnes Szávay.

In the Tier IV 2007 Estoril Open final she defeated teenager Victoria Azarenka, saving two matchpoints at 4–5 in the third set.

At the 2010 Wimbledon Championships, Arn qualified and reached the third round of a Grand Slam tournament for the first time at the age of 31.

Arn qualified for the WTA Premier tournament in Tokyo, by defeating Chan Yung-jan and Elena Baltacha.

In the main draw she then defeated fellow qualifier Laura Robson in the first round, before losing to top seed Caroline Wozniacki.

In September 2017, she reached the final of an $25k event in Balatonboglár, Hungary, losing to top seed Polona Hercog.