The Mortal Instruments is a series of six young adult fantasy novels written by American author Cassandra Clare, the last of which was published on May 27, 2014. The Mortal Instruments is chronologically the third series of a planned six in The Shadowhunter Chronicles but was the first one published. It follows Clary Fray, who interacts with a group of Nephilim known as Shadowhunters while also discovering her own heritage and her family history. The Shadowhunters protect the world of mundane/human people, who are also called mundanes or "mundies", from dark forces beyond their world. The book series falls under the young adult genre, specifically that of the paranormal romance/urban fantasy and supernatural genres.

Judith Lewis, better known by her pen name Cassandra Clare, is an American author of young adult fiction, best known for her bestselling series The Mortal Instruments.