Louis Rendu (9 December 1789 in Meyrin – 20 August 1859) was a French Roman Catholic bishop of Annecy and a scientist.

Louis Rendu was born at Meyrin, a small town a mile northwest of Geneva, on 9 December 1789.^[1]

He received his priestly education at the Grand Séminaire de Chambéry.^[2] He was ordained a priest on 19 June 1814, and appointed a teacher of belles lettres at the Collège royale de Chambéry.^[3] From 1821 to 1829, he was a professor of Physics.

He was a founding member of the Académie des sciences, belles-lettres et arts de Savoie in 1819, along with Alexis Billiet, future archbishop of Chambéry, and the society's permanent secretary.^[4]

His first book, Traité de Physique, was published at Chambéry in 1825.^[5] In 1828, he published Théorie électrique de cristallisation, which was awarded a prize by the Institut de France.^[6] In 1829, the Collège de Chambéry was handed over to the Jesuits, and Rendu was named a canon of the cathedral Chapter of Chambéry.^[7]

He was nominated bishop of Annecy by King Charles Albert of Sardinia on 25 August 1842, and approved by Pope Gregory XVI on 27 January 1843.^[8] He was consecrated a bishop in the cathedral of Annecy on 29 April 1843, by Archbishop Alexis Billiet of Chambéry.^[9] As bishop, he chose to send his best priestly students to the University of Turin, to take degrees in Canon Law,^[10] under Giovanni Nepomuceno Nuytz, until Nuytz's views were condemned by Pope Pius IX in his apostolic brief of 22 August 1851.^[11]

In a diocese which contained around 300 parishes, he built and consecrated 102 new churches.^[12]

Bishop Rendu was a Chevalier de l'Ordre du Mérite civil de Savoie, and a Commandeur de l'Ordre des SS. Maurice et Lazare.

Bishop Rendu died on 20 August 1859.^[13] His almoner, François Marie Guillermin, who was present at the death-bed, says it was 21 August.^[14]

Rendu was the author of Theorie des glaciers de la Savoie,^[15] an important book on the mechanisms of glacial motion. The Rendu Glacier, Alaska, U.S. and Mount Rendu, Antarctica are named for him.

His ethnological and religious-themed works include:

• De l'influence des Moeurs sur les Lois, et de l'influence des Lois sur les Moeurs, 1833
• Moeurs et coutumes de la Savoie du Nord au XIXe siècle, 1845
• Lettre à S. M. le Roi de Prusse (sur la situation religieuse de l'Europe), 1848
• Des efforts du protestantisme, (in French) Paris: Louis Vives 1855.^[16]
• "Mandements et instructions pastorales." (in French). Collected in: Jacques-Paul Migne, Collection intégrale et universelle des orateurs sacrés du premier et du second ordre. Volume 85. Paris: A l'imprimerie Catholique du Petit-Montrouce, 1856. Pp. 103-395.

• List of Roman Catholic scientist-clerics

• Baud, Henri; Binz, Louis (1985). Le Diocèse de Genève-Annecy. (in French). Annecy: Editions Beauchesne, 1985. Pp. 209-211.
• Guillermin, F.-M. (1867). Vie de Mgr Louis Rendu, évêque d'Annecy. (in French). Paris: C. Douniol, 1867. {reprint: Hachette 2016] [eulogistic, pietistic]
• Mermillod, Gaspard (1859). Mgr. Louis Rendu, évêque d'Annecy: esquisse biographique, (in French), Carouge: A. Jaquemot 1859.
• Ritzler, Remigius; Sefrin, Pirminus (1968). Hierarchia Catholica medii et recentioris aevi ... A pontificatu Pii PP. VII (1800) usque ad pontificatum Gregorii PP. XVI (1846) (in Latin). Vol. VII. Monasterii: Libr. Regensburgiana.

• David M. Cheney, Catholic-Hierarchy.org., "Bishop Louis Rendu"^{[self-published source]}
• Australian Antarctic Data Centre: Maps, charts, and geographic information, Mount Rendu. Retrieved: 30 July 2024.