Grigory Alexandrovich Demidov (Russian: Григорий Александрович Демидов; 21 February 1765 – 31 January 1827) was a Russian nobleman from the Demidov family.
He initially served as an adjutant to Catherine II of Russia in a guards regiment.
On 13 September 1797 he married princess Yekaterina Petrovna Lopukhina (11 April 1783-21 July 1830), daughter of Pyotr Lopukhin and his first wife, Praskovya Ivanovna Levshina.
They had six children: After his father's death in 1803 Grigory inherited a huge fortune.
He is buried in the Lazarevskoe Cemetery at the Alexander Nevsky Lavra.