Gertrude Franklin Horn Atherton (1857–1948) was an American writer.
She was born in San Francisco and lived in California all her life. She eloped with George H.B. Atherton when she was only 19, and had two children. Her husband discouraged her writing; and the serial publication of her first novel, The Randolphs of Redwoods (1882), though unsigned, scandalized her family.
After her husband's death, in 1887, she was free to pursue her writing career as a protégé of Ambrose Bierce, eventually writing 60 books and numerous articles. Atherton's first signed novel, What Dreams May Come, was published in 1888 under the pseudonym Frank Lin.
Her novels often feature strong heroines who pursue independent lives, undoubtedly a reaction to her stifling married life. She is best remembered for a series of historical novels and short stories set in California, including The Splendid, Idle Forties (1902); The Conqueror (1902), which is a fictionalized biography of Alexander Hamilton; and her sensational, semi-autobiographical novel Black Oxen (1923), about a middle-aged woman who miraculously becomes young again after glandular therapy.