Helen Hayes MacArthur (née Brown; October 10, 1900 – March 17, 1993) was an American actress. Often referred to as the "First Lady of American Theatre", she was the second person and first woman to win the EGOT (an Emmy, a Grammy, an Oscar, and a Tony Award), and the first person to win the Triple Crown of Acting. Hayes also received the Presidential Medal of Freedom, America's highest civilian honor, from President Ronald Reagan in 1986. In 1988, she was awarded the National Medal of Arts.

The annual Helen Hayes Awards, which have recognized excellence in professional theatre in greater Washington, D.C., since 1984, are her namesake. In 1955, the former Fulton Theatre on 46th Street in New York City's Theatre District was renamed the Helen Hayes Theatre. When that venue was demolished in 1982, the nearby Little Theatre was renamed in her honor. Helen Hayes is regarded as one of the greatest leading ladies of the 20th-century theatre. Her career spanned 82 years.

A leading philanthropist in later decades, Hayes was most proud of her 49-year association with the Helen Hayes Hospital, a non-profit rehabilitative center overlooking the Hudson River in West Haverstraw, NY.