Marvis Linwood "Bootsy" Thornton III (born July 30, 1977) is an American former professional basketball player.

After graduation from St. John's University, where he played for two years, Thornton moved to Italy, where he made a name for himself over the following decade.

Thornton spent his most successful years with Montepaschi Siena for which he played on three occasions, winning as many national championship titles and being an All-EuroLeague Second Team selection in 2008.

Thornton played basketball at Paul Laurence Dunbar High School, in Baltimore, Maryland.

Thornton will forever have a place in St. John's Red Storm lore, thanks to his 40-point performance against Duke on January 24, 1999, including seven three-pointers.