Orlov was the son of Gregory Orlov, governor of Great Novgorod. He had a younger brother Alexei Grigoryevich Orlov who would equally gain military and political prominence in Russia. Grigory Orlov was educated in the corps of cadets at Saint Petersburg, began his military career in the Seven Years' War, and was wounded at Zorndorf. While serving in the capital as an artillery officer, he caught the fancy of the then Grand Duchess Catherine Alekseyevna, and was the leader of the conspiracy which resulted in the dethronement and death of her husband, Emperor Peter III (1762).