The House of Demidov () also Demidoff, was a prominent Russian noble family during the 18th and 19th centuries. Originating in the city of Tula in the 17th century, the Demidovs found success through metal products, and were entered into the European nobility by Peter the Great. Their descendants became among the most influential merchants and earliest industrialists in the Russian Empire, and at their peak were predicted to be the second-richest family in Russia, behind only the Russian Imperial Family. The Demidov family lost its fortune after the February Revolution of 1917, but continues to exist under the rendering Demidoff.