Robertson K. Mygatt or 'R.K.', (1861–1919) was an American landscape painter and etcher working at the turn of the 20th century. He is often associated with the Tonalist movement which was being experimented with in painting during most of his active years, having emerged as a movement in the 1880s that continued through about 1915. R. K. Mygatt was born in New York City in 1861, where he studied at the Art Students League of New York with noted landscape artist John Henry Twachtman and American impressionist painter William Merritt Chase. He also studied painting in Europe.