Cassandra Clare, born Judith Rumelt on July 27, 1973, is a renowned American author of young adult fiction, best known for her bestselling series The Mortal Instruments.

Cassandra Clare was born in Tehran, Iran to American parents and spent much of her childhood traveling the world with her family. As a toddler, she experienced a notable trek through the Himalayas, spending a month in her father’s backpack. Before she was ten, she lived in France, England, and Switzerland. Her love for books began early, as they became her constant companions amidst her family's travels.

Clare spent her high school years in Los Angeles, where she began writing stories for her classmates. After college, she lived in Los Angeles and New York, working as an entertainment journalist. Her career in journalism was varied and included reporting for tabloids. It was while living in New York that Clare was inspired to write her debut novel, City of Bones, which became the first book in The Mortal Instruments series and a New York Times bestseller.

Cassandra Clare transitioned to writing fantasy fiction full-time in 2006. Her writing is often inspired by world mythology, and she incorporates various mythological elements into her stories. Clare prefers writing in coffee shops with friends due to her dislike of working alone at home.

In addition to her popular series, Clare's first professional writing sale was a short story titled "The Girl’s Guide to Defeating the Dark Lord" in a Baen anthology of humor fantasy. She currently resides in Massachusetts with her fiancé and their two cats.