- Author: Lyman Frank Baum
- Copyright: Public domain
- Published in: 1917
- Word count: 46,695 words (≈ about 3 hours)
The Lost Princess of Oz is the eleventh canonical Oz book written by L. Frank Baum. Published on June 5, 1917, it begins with the disappearance of Princess Ozma, the ruler of Oz and covers Dorothy and the Wizard's efforts to find her. The introduction to the book states that its inspiration was a letter a little girl had written to Baum: "I suppose if Ozma ever got hurt or losted, everybody would be sorry."