The Halle Open is a professional men's tennis tournament that is part of the ATP Tour 500 category. It has been held annually in Halle (Westfalen) since 1991 and has been a professional tournament since 1993.

It is known for sponsorship reasons as the Terra Wortmann Open since 2022, and previously as the Gerry Weber Open from 1993 to 2018 and as the Noventi Open from 2019 to 2021. It is an alternative tournament to that of Queen's London, in preparation for Wimbledon. It was voted by tennis players as the best category tournament in 2000. The 2020 edition is not being played due to the COVID-19 pandemic.

The tournament was played the week following the French Open, while since 2015 it has been played in the central week of the three that separate Roland Garros from Wimbledon and is a preparation tournament for the London Grand Slam. Played on grass courts, it was part of the ATP World Tour 250 series until 2014. As of 2015, the tournament is part of the ATP World Tour 500 series.

The center court, the Owl Arena, has a maximum capacity of 11,500 spectators, and is also used for other sports, such as basketball, volleyball and boxing. It is equipped with a mobile roof which ensures the continuation of matches even in the event of adverse weather conditions.

In the first edition of the event, in 1993, Henri Leconte defeated Andrij Medvedjev to take the trophy. Roger Federer has won the tournament ten times, as well as reaching the final three other times, including one win and one loss in the doubles final.