James Joseph "Whitey" Bulger Jr. was an American organized crime boss who led the Winter Hill Gang in the Winter Hill neighborhood of Somerville, Massachusetts, a city directly northwest of Boston. On December 23, 1994, Bulger fled the Boston area and went into hiding after his former FBI handler, John Connolly, tipped him off about a pending RICO indictment against him. Bulger remained at large for sixteen years. After his 2011 arrest, federal prosecutors tried Bulger for nineteen murders based on grand jury testimony from Kevin Weeks and other former criminal associates.

The Winter Hill Gang was a loose confederation of organized crime figures in the Boston, Massachusetts, area. It is generally considered an Irish Mob organization, with most gang members and the leadership consisting predominantly of Irish-Americans, though some notable members, such as Johnny Martorano, are of Italian-American descent.