information:classification, structural:expansion
Birth and family background

Blavatsky was born as Helena Petrovna Hahn von Rottenstern in the town of Yekaterinoslav, then part of the Russian Empire. Her birth date was 12 August 1831, although according to the Julian calendar used in 19th-century Russia it was 31 July. Immediately after her birth, she was baptized into the Russian Orthodox Church. At the time, Yekaterinoslav was undergoing a cholera epidemic, and her mother contracted the disease shortly after childbirth; despite the expectations of their doctor, both mother and child survived the epidemic.

Blavatsky's family was aristocratic. Her mother was Helena Andreyevna Hahn von Rottenstern (Russian: Елена Андреевна Ган, 1814–1842; née Fadeyeva), a self-educated 17-year-old who was the daughter of Princess Yelena Pavlovna Dolgorukaya, a similarly self-educated aristocrat. Blavatsky's father was Pyotr Alexeyevich Hahn von Rottenstern (Russian: Пётр Алексеевич Ган, 1798–1873), a descendant of the German Hahn aristocratic family, who served as a captain in the Russian Royal Horse Artillery, and would later rise to the rank of colonel. Pyotr had not been present at his daughter's birth, having been in Poland fighting to suppress the November Uprising against Russian rule, and first saw her when she was six months old. As well as her Russian and German ancestry, Blavatsky could also claim French heritage, for a great-great grandfather had been a French Huguenot nobleman who had fled to Russia to escape persecution, there serving in the court of Catherine the Great.

As a result of Pyotr's career, the family frequently moved to different parts of the Empire, accompanied by their servants, a mobile childhood that may have influenced Blavatsky's largely nomadic lifestyle in later life. A year after Pyotr's arrival in Yekaterinoslav, the family relocated to the nearby army town of Romankovo. When Blavatsky was two years old, her younger brother, Sasha, died in another army town when no medical help could be found. In 1835, mother and daughter moved to Odessa, where Blavatsky's maternal grandfather Andrei Fadeyev, a civil administrator for the imperial authorities, had recently been posted. It was in this city that Blavatsky's sister Vera Petrovna was born.