Thirty Day Princess is a 1934 pre-Code comedy film directed by Marion Gering and starring Sylvia Sidney, Cary Grant and Edward Arnold.

The film was based on a story of the same name by Clarence Budington Kelland (which appeared in Ladies' Home Journal in 1933),[1] adapted by Sam Hellman and Edwin Justus Mayer, and written by Preston Sturges and Frank Partos.

On her way to New York to find financial backing for her impoverished country, the Ruritanian Kingdom of Taronia, Princess "Zizzi" Catterina (Sylvia Sidney) falls ill with the mumps and has to be quarantined for a month.

Production on Thirty Day Princess was to have begun on 28 February 1934, but was delayed because of the illness of William Collier Sr., who was scheduled to play the role of the "Managing editor".

[4] Mordaunt Hall of The New York Times wrote, "This amiable light affair has a generous share of imaginative turns, and it is further endowed with a highly competent supporting cast.