The Mystery of the 99 Steps
| Author | Carolyn Keene |
|---|---|
| Language | English |
| Series | Nancy Drew Mystery Stories |
| Genre | Juvenile literature |
| Publisher | Grosset & Dunlap |
Publication date | 1966 |
| Publication place | United States |
| Media type | Print (hardback & paperback) |
| Preceded by | The Phantom of Pine Hill |
| Followed by | The Clue in the Crossword Cipher |
The Mystery of the 99 Steps is the forty-third volume in the Nancy Drew Mystery Stories series. It was first published in 1966 under the pseudonym Carolyn Keene. The actual author was ghostwriter Harriet Stratemeyer Adams.