Joseph Albert "Jock" Yablonski (March 3, 1910 – December 31, 1969) was an American labor leader in the United Mine Workers in the 1950s and 1960s known for seeking reform in the union and better working conditions for miners. In 1969 he challenged Tony Boyle for the presidency of the international union and was defeated. He asked for a Department of Labor (DOL) investigation, charging a fraudulent election. In addition, Yablonski filed suit against the UMWA on five different charges related to fraud. On New Year's Eve, Yablonski, his wife and 25-year-old daughter were murdered, fatally shot at home by three gunmen found to have been hired on orders of Tony Boyle.