[1] After defeating Liu Wei in his first match in the welterweight division of the 2016 Summer Olympics he lost a 3-0 decision to eventual silver medalist (and 2017 World Amateur Champion) Shakhram Giyasov of Uzbekistan.

[3] Stanionis notched three more victories in 2017, stopping Isaac Freeman on July 30,[4] Oscar Valenzuela on September 23,[5] and winning a unanimous decision against Todd Manuel on October 14.

He followed this up with a third-round technical knockout of Erick Daniel Martinez on June 16, and by winning a unanimous decision against Levan Ghvamichava on August 24.

He first won a unanimous decision against Samuel Figueroa on March 9, 2019, which was followed by stoppage victories over Evincii Dixon on October 26, and Julio Cesar Sanchez on December 21.

[10] Stanionis was scheduled to face the one-time WBO light welterweight title challenger Thomas Dulorme on April 10, 2021, in his first twelve-round bout.