The 2021 NÖ Open was a professional tennis tournament played on clay courts. It was the first edition of the tournament which was part of the 2021 ATP Challenger Tour. It took place in Tulln an der Donau, Austria between 6 and 12 September 2021.
Singles main-draw entrants
Seeds
1 Rankings are as of 30 August 2021.
Other entrants
The following players received wildcards into the singles main draw: Gerald Melzer Filip Misolic Lukas Neumayer
The following players received entry into the singles main draw as alternates: Johannes Härteis Lucas Miedler
The following players received entry from the qualifying draw: Benjamin Hassan Uladzimir Ignatik Matteo Martineau Neil Oberleitner
Champions
Singles
Mats Moraing def. Hugo Gaston 6–2, 6–1.
Doubles
Dustin Brown / Andrea Vavassori def. Rafael Matos / Felipe Meligeni Alves 7–6(7–5), 6–1.