Marlys Joy Millhiser was an American author known for her works in the mystery and horror genres. Her most acclaimed novel, The Mirror, was published in 1978. She also authored other notable works such as The Threshold, Michael's Wife, Nella Waits, and Willing Hostage.

Originally from Charles City, Iowa, Millhiser pursued a career as a high school teacher before venturing into the literary world. She lived much of her life in Boulder, Colorado, where she contributed significantly to the field of mystery writing. Millhiser also served as the regional vice president of the Mystery Writers of America.

She passed away on April 20, 2017, leaving behind a legacy of intriguing and suspenseful storytelling.