The princedom of San Donato was created by Leopold II, Grand Duke of Tuscany, for the Russian Italophile Anatole Demidov in 1840, so that Demidov could marry Mathilde Bonaparte without her losing her title of Princess.
The title was never recognised in Russia. It was named after Villa San Donato, the Demidov family's villa near Florence.
Anatole
Paul
Elim
Anatoly Pavlovich