Cassandra Clare, born Judith Rumelt, is an American author known for her young adult fiction, most notably the bestselling series The Mortal Instruments. She was born on July 27, 1973, in Tehran, Iran, to American parents and spent much of her childhood traveling the world, including living in France, England, and Switzerland.

Clare's early exposure to diverse cultures and locations inspired her love for books, which she carried everywhere. She wrote her first stories in high school, often inspired by friends and classic literature, including her pen name's inspiration, Jane Austen's "The Beautiful Cassandra." After completing college, she worked in Los Angeles and New York as a journalist before turning to fiction.

Her debut novel, City of Bones, part of The Mortal Instruments series, was published in 2007, marking her full-time transition to writing. Clare's works are set in richly imagined fantasy worlds, blending mythology from various cultures with her own creative ideas. She frequently works in coffee shops alongside friends to stay productive.

Cassandra Clare is currently based in Massachusetts with her fiancé and two cats, continuing to write and expand her series, which include The Infernal Devices and The Dark Artifices.