The cause was cancer, the Associated Press reported.
Ms. Loudon won a 1977 Tony Award for Annie. As Miss Hannigan, the tippling mistress of a dank city orphanage, she first abused Little Orphan Annie, then tried to steal her away from the loving and rich Daddy Warbucks in hopes of a reward. She delighted audiences nightly with her comic-sour ode to "Little Girls." She shared a second rousing number, "Easy Street," with the characters of Rooster, Hannigan's conniving brother, and Lily St. Regis, Rooster's dim floozy girlfriend.
A blowsy, big-voiced, big-haired, big-eyed presence, Ms. Loudon did not shy from generous performances. She was in many ways a creature of the stage, where, despite appearing in a high number of flops, she found her greatest success.
According to the New York Post, Loudon landed the role of Hannigan only by chance, after a chance encounter Mike Nichols, who was Annie's producer. The two had known each other from their early cabaret days in Manhattan, and Nichols had directed her in her stage debut, an Off-Broadway production of World of Jules Feiffer. Nichols suggested the then-out-of-work actress audition. She did, and won the job.
Annie proved the culmination of a long, hit-and-miss career. Though she went on to a few more noteworthy parts—she played opposite Katharine Hepburn in West Side Waltz in 1981 and starred in the original Broadway production of Noises Off in 1983—she never again found a vehicle as good or successful as Annie. In recent years, she was seldom seen on the New York stage. Ms. Loudon was announced to act in Dinner at Eight last season at Lincoln Center Theater, but bowed out during previews. Marian Seldes took over. A few recent projects did not completely flower. In 1998, Varese Sarabande Records released a concept recording of a musical based on the film The Night of the Hunter, on which Ms. Loudon sang a role. No production resulted in the actress' lifetime. The next year, she acted at Signature Theatre of Virginia's world premiere of Over & Over, the John Kander and Fred Ebb musicalization of The Skin of Our Teeth. The show did not go beyond that staging and remains in development.
Dorothy Loudon was born Sept. 17, 1933, in Boston, MA, and went to school at the American Academy of Dramatic Arts. Her first love was dancing. "I used to walk around with a turban and tap shoes, and I took tap-dancing lessons," she told Playbill's Harry Haun in one of her last interviews. "Then, for some reason, when I went to college, I thought `Dancers are very disciplined, and I don't want to live that hard life,' so I got a drama scholarship to Syracuse and did a lot of acting there. That's really all I wanted to do from that point on."
She first attracted national attention on television's "Gary Moore Show," where she replaced Carol Burnett (who would later get the Miss Hannigan role in the movie of Annie).
The actress made her Broadway debut in the revue Nowhere to Go But Up. The 1962 show lasted only a week, but Ms. Loudon won good notices and a Theatre World Award. Also short-lived were 1968's Noel Coward's Sweet Potato, 1969's The Fig Leaves Are Falling (for which she nonetheless received a Tony nomination and a Drama Desk Award) and 1969's revival of Three Men on a Horse (another Drama Desk Award).
She won a third Tony nomination for 1978's Ballroom, the Michael Bennett musical which lasted only a few months.
Her success in Annie led to a short-lived 1979 television series called "Dorothy," in which she played a former Broadway star who teaches at an all-girl school in Connecticut.
Touring engagements included a stint in the Harold Prince-directed Show Boat.
Ms. Loudon was married to Norman Paris, a musician and composer, in 1971. He died in 1977, during her run in Annie; she left the show shortly thereafter. She is survived by two stepchildren.
The comedienne displayed her ability to seize a comic moment with the best of them on opening night of the New York run of West Side Waltz. "Opening night we were doing a scene and the phone rang and it wasn't supposed to ring," Ms. Loudon recalled. "[Katharine Hepburn and I] both just sort of stared at it. Katharine was closest to it so she went over and picked it up and she say in that marvelous voice, `Hello?' And then she held it out to me and said, `It's for you.' I went over and took the phone and put the receiver to my ear and said, `Well, whoever it was hung up.'"