John Lawrence Sullivan, known simply as John L. among his admirers, and dubbed the "Boston Strong Boy" by the press, was an American boxer. He is recognized as the first heavyweight champion of gloved boxing, de facto reigning from February 7, 1882, to September 7, 1892. He is also generally recognized as the last heavyweight champion of bare-knuckle boxing under the London Prize Ring Rules, being a cultural icon of the late 19th century America, arguably the first boxing superstar and one of the world's highest-paid athletes of his era. Newspapers' coverage of his career, with the latest accounts of his championship fights often appearing in the headlines, and as cover stories, gave birth to sports journalism in the United States and set the pattern internationally for covering boxing events in media, and photodocumenting the prizefights.

Bare-knuckle boxing is a full-contact combat sport based on punching without any form of padding on the hands. The sport as it is known today originated in 17th-century England and differs from street fighting as it follows an accepted set of rules.