Gertrude Franklin Horn Atherton (October 30, 1857 – June 14, 1948) was a prominent and prolific American author. Many of her novels are set in her home state of California. Her bestseller Black Oxen (1923) was made into a silent movie of the same name. In addition to novels, she wrote short stories, essays, and articles for magazines and newspapers on such issues as feminism, politics, and war. She was strong-willed, independent-minded, and sometimes controversial.

She wrote using the pen names Asmodeus and Frank Lin, a play on her middle name.