Leonhard Baldner (1612 – 1 February 1694) was a Strasbourg fisherman and naturalist who wrote an illustrated book on the fishes, birds, and mammals in 1666 titled Vogel-, Fisch- und Thierbuch of which only five manuscript copies are now known to exist. 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.
The exact date of birth of Baldner is unknown but he was born in an old fisher family in Strasbourg. He married Salome, daughter of Hans Michael Fries on January 25, 1636 and had four children. He married his second wife Anna Ursula, daughter of a goldsmith, Abraham Sprengel in 1650 and they had four children while working as a toll collector. He later became a forester and then a forest manager. After the death of his second wife, he married Barbara, daughter of Benedictus Grossen, a professor of Hebrew. They too had four children of whom the youngest son, Andreas born in February 1673 transcribed the manuscripts of his father. Baldner died on February 1, 1694 and is buried in the Saint-Urbain cemetery in Strasbourg.
A facsimile edition of Baldner's MS was published by Robert Lauterborn in 1903 although there are slight differences between the plates among the various surviving manuscript editions. It included three parts; the first on birds included 68 species while the second dealt with 45 fishes and crustaceans. The third part included quadrupeds and other animals. His writings were based on personal observation and he did not rely on reports by others. He hired a Strasbourg artist, Johann Georg Walther, to illustrate the book. An MS copy was obtained by Francis Willughby in 1663 and some notes were cited by John Ray.
- Fluck, Hans-R.; Scharbach, Albert (2016). "« Leonhard Baldner – Zu seinem Testament und Nachlassverzeichnis »". Revue d’Alsace. 142. doi:10.4000/alsace.2550.
- Geus, Armin (1964). "Leonhard Baldner, a Strasbourg Fisherman". Isis. 55 (2): 195. doi:10.1086/349828. JSTOR 28185.
- "Leonhard Baldner: Vogel—, Fisch- und Thierbuch, 1666. Handschrift Ms20 phys. Et hist. Nat. 3 der Murhardschen Bibliothek der Stadt Kassel und Landesbibliothek. Faksimileausgabe mit über 130 ganzseitigen Aquarellen, rd. 400 Seiten in 2 Bänden. Mit zwei Beiheften: Einführung von Robert Lauterborn (63 S.) und Erläuterungen zu den Tafeln von Robert Lauterborn, Horst Janus und Claus König (40 S.). Stuttgart: Verlag Müller und Schindler 1973. DM 640,—". Internationale Revue der gesamten Hydrobiologie und Hydrographie. 71: 150. 1986. doi:10.1002/iroh.19860710131.
- Nellen, Walter; Dulčić, Jakov (2008). "Evolutionary steps in ichthyology and new challenges". Acta Adriatica. 49 (3): 201–232.
- Birkhead, Tim (2016). Virtuoso by Nature: The scientific worlds of Francis Willughby FRS (1635-1672). Brill. p. 195.
- Phillips, John C. (1925). "Leonard Baldner, Seventeenth Century Sportsman and Naturalist. An Unrecorded Copy of His Book, Containing His Portrait" (PDF). The Auk. 42 (3): 332–341.