The 2021 İstanbul Cup (also known as the TEB BNP Paribas Tennis Championship İstanbul for sponsorship reasons) is a tennis tournament played on outdoor clay courts.

It is the 14th edition of the İstanbul Cup, and part of the WTA International tournaments of the 2021 WTA Tour.

It took place in Istanbul, Turkey, from 19 through 25 April 2021.

[1] The following players received wildcards into the singles main draw: The following players received entry from the qualifying draw: The following player received entry as a lucky loser: The following pairs received wildcards into the doubles main draw: The following pairs received entry using protected rankings: