John Ulrich Giesy (1877-1947) was an American physician and writer. One of the pioneers of the Sword and Planet genre, Giesy published in several popular magazines, and his Jason Croft series enjoyed wide popularity in the early decades of the 20th century. He wrote much speculative fiction, including future history, science fiction, fantasy, and sword and planet ficiton. Giesy's career and popularity waned in the 1930s; he died in Salt Lake City in 1947.
