The 2021 Karlsruhe Open (also known as the Liqui Moly Open for sponsorship reasons) was a professional tennis tournament played on outdoor clay courts.

It was the 2nd edition of the tournament and part of the 2021 WTA 125K series, offering a total of $115,000 in prize money.

It took place in Karlsruhe, Germany between 7 and 12 September 2021.

The tournament did not take place in 2020 due to the COVID-19 pandemic.

[1] The following players received a wildcard into the singles main draw: The following players qualified into the singles main draw: The following pair received a wildcard into the doubles main draw: