Nadezhda Yakovlevna Mandelstam (Russian: Надежда Яковлевна Мандельштам, née Hazin; 31 October 1899 – 29 December 1980) was a Russian writer and a wife of poet Osip Mandelstam.

Born in Saratov into a middle-class Jewish family, she spent her early years in Kiev. After the gymnasium she studied art.

After their marriage in 1921, Nadezhda and Osip Mandelstam lived in Ukraine, Petrograd, Moscow, and Georgia. Osip was arrested in 1934 for his Stalin Epigram and exiled with Nadezhda to Cherdyn, in the Perm region and later to Voronezh.

After Osip Mandelstam's second arrest and his subsequent death at a transit camp "Vtoraya Rechka" near Vladivostok in 1938, Nadezhda Mandelstam led an almost nomadic way of life, dodging her expected arrest and frequently changing places of residence and temporary jobs. On at least one occasion, in Kalinin, the NKVD came for her the next day after she fled.

As her mission in life, she set to preserve and publish her husband's poetic heritage. She managed to keep most of it memorized because she did not trust paper.

After the death of Stalin, Nadezhda Mandelstam completed her dissertation (1956) and some years after was allowed to return to Moscow (1964).

In her memoirs, Hope Against Hope and Hope Abandoned, first published in the West, she gives an epic analysis of her life and criticizes the moral and cultural degradation of the Soviet Union of the 1920s and later. The titles of her memoirs are puns, Nadezhda in Russian meaning "hope".

In 1976 she gave her archives to Princeton University. Nadezhda Mandelstam died in 1980 in Moscow, aged 81.

Hope Against Hope was first published in English in 1970. It is Nadezhda Mandelstam's memoir of her life with Osip, who was first arrested in 1934 and died in Stalin's Great Purge of 1937-38. Hope Against Hope is a vital eyewitness account of Stalin's Soviet Union and one of the greatest testaments to the value of literature and imaginative freedom ever written. But it is also a profound inspiration - a love story that relates the daily struggle to keep both love and art alive in the most desperate circumstances.