Peter Duncan Lerangis is an American author of children's and young adult fiction, best known for his Seven Wonders series and his contributions to The 39 Clues series.

His work includes The Viper's Nest and The Sword Thief, two titles in the children's-book series The 39 Clues, the historical novel Smiler's Bones, the YA dark comedy-adventure novel wtf, the Drama Club series, the Spy X series, the Watchers series, the Abracadabra series, and the Antarctica two-book adventure. He has also ghostwritten for series such as The Three Investigators, The Hardy Boys Casefiles, Sweet Valley Twins, and more than forty books in the series The Baby-sitters Club and its various spin-offs.

Lerangis has written novels based on film screenplays, including The Sixth Sense, Sleepy Hollow, and Beauty and the Beast, as well as five video game novelizations in the Worlds of Power series created by Seth Godin.