Mary Downing Hahn (born December 9, 1937) is an American writer of young adult novels and former school librarian. She is known for many books such as Stepping On The Cracks and Wait Till Helen Comes. She published her first book in 1979 and has since written over twenty novels.
- Scott O'Dell Award for Historical Fiction for Stepping on the Cracks (1992, won)
- Mystery Writers of America Edgar Award for Closed for the Season (2010, won)
On the 12th September 2014, Variety announced that financing and cast were in place and principal photography would commence on the production of a film adaptation of Wait Till Helen Comes. The work would be directed by Dominic James, and would star Maria Bello and the Nélisse sisters. Production was slated to begin later that same month. Principal photography began on the 28th September 2014 in Winnipeg, Manitoba. Author Mary Downing Hahn appears in the film in a speaking role, mentioning to one of the producers that as a little girl she had always wanted to be an actress in movies. This is the first of her books to be adapted into a feature film. As of the 7th May 2015, the motion picture version of Wait Till Helen Comes is in post-production. It is contemplated that it will be released in 2016.