Helisaeus Roeslin or Helisäus Röslin (17 January 1545 – 14 August 1616) was a German physician and astrologer who adopted a geoheliocentric model of the universe. He was one of five observers who concluded that the Great Comet of 1577 was located beyond the moon. His representation of the comet, described as "an interesting, though crude, attempt," was among the earliest and was highly complex.