Lillian Mathilde Genth (born Philadelphia, 1876; died New York City, 1953) was a United States artist.
She studied art at the Philadelphia School of Design for Women, and under Whistler at Paris. She returned to the United States in 1903. She painted many female nudes with landscape backgrounds and also several portraits. She was awarded the Mary Smith prize in 1904, the Shaw memorial prize in 1907 and the Hallgarten prize of the National Academy in 1911. She is represented in the National Gallery, Washington, D.C., the Carnegie Institute, Pittsburgh, the Brooklyn Institute Museum, and the Metropolitan Museum of Art, New York. In 1908 she was elected into the National Academy of Design as an Associate Academician.