The PFL 4 mixed martial arts event for the 2021 season of the Professional Fighters League was held on June 10, 2021. This was the fourth regular season event of the tournament and included fights in the Featherweight and Lightweight divisions. Boxing champion and Olympic gold medalist Claressa Shields made her MMA debut in the main event against Brittney Elkin.

The PFL 1 mixed martial arts event for the 2021 season of the Professional Fighters League was held on April 23, 2021. This was the first regular season event of the tournament and included fights in the Featherweight and Lightweight divisions. The event was headlined by a lightweight clash between the former UFC and WEC Lightweight champion Anthony Pettis and the UFC veteran Clay Collard.

EFN: Battle Of Moscow 9: Unbreakable was a mixed martial arts and kickboxing event held by Fight Nights Global on December 16, 2012 at the Dynamo Sports Palace in Moscow, Russia.

Fedor vs. Maldonado was a mixed martial arts event held by Eurasia Fight Nights Global on June 17, 2016 at the Sibur Arena in Saint Petersburg, Russia.

In the main event, former UFC heavyweight champion Junior dos Santos will square off against fellow UFC veteran Yorgan De Castro in a heavyweight contest. Dos Santos will be competing for the first time since his departure from the UFC in early 2021. De Castro won his Eagle FC debut in January with a first-round guillotine over Shaun Asher in 64 seconds.