Lydia Dan
| Lydia Osipovna Dan | |
|---|---|
| Lydia Dan (centered), with Semyon Vainshtein (left) and Irakli Tsereteli (right) Irkutsk (1914–1915). | |
| Born | Lydia Osipovna Tsederbaum May 21, 1878. | 
| Died | March 28, 1963 (aged 84) New York City, New York, United States | 
| Occupation | Menshevik revolutionary | 
| Spouse | Fyodor Dan | 
Lydia Osipovna Dan (Russian: Ли́дия О́сиповна Дан; née Tsederbaum; 21 May 1878 – 28 March 1963) was a Menshevik revolutionary leader and active participant in the revolutionary movement of Russia.
Her brother was the Menshevik leader Julius Martov, her husband was fellow Menshevik Fyodor Dan.