The 2021 Stockholm Open was a professional men's tennis tournament played on indoor hard courts.

It took place at the Kungliga tennishallen in Stockholm, Sweden from 7 to 13 November 2021.

Unseeded Tommy Paul won the singles title.

[2] Paul won his first ATP Tour title.

[3] The following players received wildcards into the singles main draw: The following players received entry from the qualifying draw: The following players received entry as lucky losers: The following pairs received wildcards into the doubles main draw: The following pairs received entry into the doubles main draw as alternates: