Sister Gwen Hennessey, O.S.F., (born September 29, 1932) is a Roman Catholic Franciscan Order Sister and activist. She was born on a farm in Buchanan County, Iowa, the thirteenth child of Anna Killias Hennessey and Maurice Hennessey. After residing at a religious center in Dubuque, Iowa, she now resides in Sioux City, Iowa
She is most widely known for protests at Fort Benning, Georgia, home of the Army's School of the Americas, a facility for training Latin American soldiers. Gwen Hennessey, along with her natural sister, Sister Dorothy Hennessey, O.S.F., were both arrested and convicted to six months in jail for their protest in 2001.
Hennessey believes that the School of the Americas teaches torture techniques to Latin American soldiers, and that graduates of the program have been involved in atrocities, including the 1989 murders of six Jesuit priests and two women in El Salvador. The school denies these claims and argues that it helps to spread democracy in Latin America.
She took part in a protest march in the 1960s in Antioch, Illinois. African Americans were banned from the city, and Martin Luther King, Jr. was marching with her. She also helped Cesar Chavez, leader of the United Farm Workers, organize migrant workers in California.
In 2002, Gwen Hennessey, along with her sister Dorothy Hennessey, was awarded the Pacem in Terris Award. It was named after a 1963 encyclical letter by Pope John XXIII that calls upon all people of good will to secure peace among all nations. Pacem in terris is Latin for 'Peace on Earth'.
Hennessey now serves as the director of the Clare Guest House, in Sioux City.