Vasyl Anatoliyovych Lomachenko (Ukrainian: Василь Анатолійович Ломаченко, IPA: [wɐˈsɪlʲ lomɐˈtʃɛnko]; also spelled Vasiliy; born 17 February 1988) is a Ukrainian professional boxer. He is a former world champion in three weight classes, having held the WBO featherweight title from 2014 to 2015; the WBO junior lightweight title from 2016 to 2017; and the unified WBA (Super), WBC, WBO and Ring magazine lightweight titles between 2018 to October 2020.

Lomachenko is one of the most successful amateur boxers of all time, possessing a record of 396 wins and 1 loss, with that loss avenged twice. Competing in the featherweight and lightweight divisions, he won a silver medal at the 2007 World Championships, gold at the 2008 European Championships, consecutive gold at the 2008 and 2012 Olympics, and consecutive gold at the 2009 and 2011 World Championships. He is known for his exceptional hand speed, timing, accuracy, creativity, athleticism, defense and footwork.

Lomachenko made his professional debut in 2013. He ties the record with Saensak Muangsurin for winning a world title in the fewest professional fights, winning the WBO featherweight title in his third fight. All of his professional fights except the debut were world championship fights. He made his first main event in the second professional fight.

He has won several awards by media outlets throughout his career. The Ring and ESPN named him Prospect of the Year in 2013; CBS Sports named him Boxer of the Year in 2016; HBO Sports named him Boxer of the Year in 2016 and in 2017; the Boxing Writers Association of America and The Ring named him Fighter of the Year in 2017.

As of October 2020, Lomachenko is ranked as the world's second best active boxer, pound for pound, by Boxing Writers Association of America, sixth by ESPN, seventh by The Ring and tenth by the TBRB. He is also ranked as the world's second best active lightweight by BoxRec, the Transnational Boxing Rankings Board (TBRB), The Ring magazine and ESPN.