Leonhard Baldner or Leonard Baltner (1612 – 1 February 1694) was a Strasbourg fisherman and naturalist who produced a hand-written illustrated book on the fishes, birds, and mammals titled Vogel-, Fisch- und Thierbuch. Only six manuscript copies are now known to exist, two are dated 1653 and the other four 1666. He was one of the early pioneers to use glass aquariums to study fish in life. He was also possibly the first to write on the migration and life-history of the salmon.