John William Flannagan Jr. (February 20, 1885 – April 27, 1955) was an American politician of the Democratic Party. He represented Virginia in the United States House of Representatives from 1931 - 1949. The John W Flannagan Dam is named after him.^[1]

Flannagan born on a farm near Trevilians, in Louisa County, Virginia. He earned a law degree from Washington and Lee University in 1907 and was admitted to the bar the same year. He practiced law for several years, before becoming the Commonwealth's attorney for Buchanan County, Virginia in 1916 and 1917. After that, Flannagan continued the practice of law, but also engaged in banking from 1917 to 1930.

Flannagan was subsequently elected as a Democrat to the 72nd Congress and to the eight succeeding Congresses (March 4, 1931 – January 3, 1949). He was the chairman of Committee on Agriculture (Seventy-eighth and Seventy-ninth Congresses), and the congressional adviser to the first session of the Food and Agriculture Organization of the United Nations at Quebec in 1945. Flannagan was not a candidate for renomination in 1948, and he resumed the practice of law in Bristol, Virginia until his death there April 27, 1955. He is interred in Mountain View Cemetery.