Mary Elizabeth McDonough, sometimes credited as Mary Beth McDonough, is an American actress and writer, best known for her role as Erin Walton on The Waltons from 1972 to 1981.

The Waltons is an American historical drama television series about a family in rural Virginia during the Great Depression and World War II. It was created by Earl Hamner Jr., based on his 1961 book Spencer's Mountain and the 1963 film of the same name. The series aired from 1972 to 1981.