Grigory Gagarin was born in Saint Petersburg to the noble Rurikid princely Gagarin family. His father, Prince Grigory Ivanovich Gagarin (Saint Petersburg, 17 March 1782 - Tegernsee, 12 February 1837), was a Russian diplomat in France and later the ambassador to Italy. His father married in Saint Petersburg in 1809 his mother Yekaterina Petrovna Sojmonova (Saint Petersburg, 23 May 1790 - Moscow, 27 February 1873). Thus until the age 13 the boy was with his family in Paris and Rome and then studied in the collegium Tolomei in Siena. Grigory did not receive a formal artistic education, but took private lessons from the famous Russian painter Karl Briullov who at that time lived in Italy.