Georg Johann Mattarnovi (Russian: Георг Иванович Маттарнови, Georg Ivanovich Mattarnovi; died 2 November 1719) was a German Baroque architect and sculptor, notable for his work in Saint Petersburg. The birthplace of Mattarnovi is unknown, but most probably it was Prussia. His year of birth is also unknown. He was a sculptor, and a disciple and assistant of German architect Andreas Schlüter. Mattarnovi arrived in Saint Petersburg in 1714, following Schlüter. After the death of Schlüter, Mattarnovi continued work on Schlüter's projects.