Leopold Pfaundler von Hadermur (14 February 1839 – 6 May 1920) was an Austrian physicist and chemist born in Innsbruck. He was the father of pediatrician Meinhard von Pfaundler (1872-1947), and the father-in-law of pediatrician Theodor Escherich (1857-1911).

He studied under chemist Heinrich Hlasiwetz (1825-1875) at Innsbruck, with Justus von Liebig (1803-1873) at the University of Munich, and with Henri Victor Regnault (1810-1878) and Charles Adolphe Wurtz (1817-1884) in Paris. In 1861 he received his doctorate, and in 1867 was appointed professor of physics at the University of Innsbruck. In 1891 he succeeded Ludwig Boltzmann (1844-1906) as professor of physics at the University of Graz. In 1887 he became a full member of the Vienna Academy of Sciences.^[1][2]

Pfaundler is remembered today for his kinetic-molecular explanation of gas reactions under the condition of equilibrium.^[3] He was the inventor of a number of scientific apparatuses — devices he often utilized in classroom demonstrations. These included a temperature regulator (1863), a Stromkalorimeter (1869), a differential air thermometer (1875), a seismograph (1897) and a distance meter (1915), to name a few.^[2] He is also credited with creating a device for optical demonstration of Lissajous figures (1873).^[4]

In 1863-64 he performed a survey of the Stubaier Alps with Ludwig Barth zu Barthenau (1839-1890), and in 1864 he was the first person to ascend to the summit of the Hofmannspitze (3112m).^[5]

• Die Physik des täglichen Lebens, gemeinverständlich dargestellt (1906).
• Die physik des täglichen Lebens mit 467 Abbildungen (1913).
• Ueber die Wärmekapazität des Wassers und eine Methode den Ort ihres Minimums zu messen (1915).
• Ueber einen neuen Distanzmesser (1915).
• Chronik der Familie Pfaundler von 1486 bis 1915 (1915).
• Die Innsbrucker Studenten-Kompagnie 1859 und 1866 (1917).
• Das chinesisch-japanische GO-Spiel: eine systematische Darstellung und Anleitung zum Spielen desselben.^[6]

He also published Müller-Pouillet's Lehrbuch der Physik und Meteorologie ("Johann Heinrich Jakob Müller–Claude Pouillet's textbook of physics and meteorology"), (9th edition, 1886–98, 3 volumes).^[7]

Pfaundler’s 1867 publication entitled “Beiträge zur chemischen Statik” [“A Contribution to Chemical Statics”]^[8][9] was a major contribution to the kinetic theory of chemical reactions.^[10] This publication was honored by a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society presented to the University of Innsbruck in 2016.^[11][12]