Marcin Knackfus (; ), was an architect, professor, and military captain from the PolishâÂÂLithuanian Commonwealth.
He was first person to introduce Neoclassical architecture in Lithuania. He designed several important buildings in Vilnius, the capital and largest city of Lithuania.
Marcin Knackfus was born in Wólka Ostroà ¼eà Âska, Kingdom of Poland, near the city of Garwolin. His date of birth is not known but is estimated based on the assumption that he was around 25 years old in 1767 when his first child was born and when he joined the Grand Ducal Lithuanian Army as construction engineer. He held the rank of captain. Knackfus first moved to Vilnius around 1768.
Knackfus studied architecture in Warsaw and was influenced by other local architects of late Baroque (Ephraim Schröger and Szymon Bogumià  Zug) and early Neoclassicism (Domenico Merlini and Johann Christian Kammsetzer). Knackfus taught at the Lithuanian Engineering Corps military school from 1769 until 1773 before becoming the first professor of architecture at Vilnius University until 1777.
In April 1771, Bishop of Vilnius Ignacy Jakub Massalski ordered Knackfus to survey a corner of the Vilnius Cathedral that had been damaged after a front tower of the cathedral collapsed in 1769. He drew up blueprints of the reconstruction, and after five reconstruction attempts, the cathedral was rebuilt in 1777 under the supervision of Polish-Lithuanian architect and former student of Knackfus, Laurynas GuceviÃÂius.
In 1773, Knackfus became an architect of the Commission of National Education and prepared projects for schools. From 1788 on, Knackfus mostly designed reconstruction projects for the city of Vilnius as well as residences for Lithuanian nobles. These include the homes of Heinrich de Reuss LXIII, the à Âopacià Âski family, Andrzej Abramowicz, and Antoni Tyzenhaus. Knackfus worked with numerous nobles, including Vilnius bishops Ignacy Jakub Massalski and Ignacy Krasicki, Field Hetman Ludwik Tyszkiewicz, voivode Karol Stanisà Âaw Radziwià Âà Â, Adam Kazimierz Czartoryski, and Grand Marshal Stanisà Âaw Lubomirski.
Knackfus married Agnieszka Pawà Âowska in 1767. They had two children, Joachim and Katarzyna.
Knackfus was a freemason and was a member of three Masonic lodges in Vilnius. Through his masonic connections, he became a supporter of Tadeusz Koà Âciuszko and the 1794 Koà Âciuszko Uprising. Upon the failure of the uprising, Russian forces stormed Vilnius and burnt down many buildings in the Sereikià ¡kÃÂs area of Vilnius where Knackfus lived. Fearing retribution for his involvement, Knackfus moved to the Suwaà Âki Region on the LithuaniaâÂÂPoland border.
He died in Vilnius .