Mirren was born Elena Lydia Mironov on 26 July 1945 at Queen Charlotte's and Chelsea Hospital in the Hammersmith district of London, to an English mother and Russian father. Her mother, Kathleen "Kitty" Alexandrina Eva Matilda (née Rogers; 1908–1996), was a working-class woman from West Ham, the thirteenth of fourteen children born to a butcher whose own father was the butcher to Queen Victoria. Mirren's father, Vasily Petrovich Mironoff (1913–1980), was a member of an old exiled family of the Russian nobility dating back to the first half of the 15th century; he was taken to England when he was two by his father, Pyotr Vasilievich Mironov (1880–1957). Pyotr Vasilievich Mironov owned a large family estate near Gzhatsk (now Gagarin) in the Russian Empire. His mother, Mirren's great-grandmother, was Countess Lydia Andreevna Kamenskaya (1848–1928), an aristocrat and a descendant of Count Mikhail Fedotovich Kamensky, a prominent Russian general in the Napoleonic Wars. Her grandfather, Pyotr Vasilievich Mironov, also served as a colonel in the Imperial Russian Army and fought in the 1904 Russo-Japanese War. He later became a diplomat in the service of Nicholas II and was negotiating an arms deal in Britain when he and his family were stranded by the Russian Revolution in 1917. He settled in London and became a cab driver to support his family.
Vasily Mironoff also played the viola with the London Philharmonic Orchestra before World War II. He was an ambulance driver during the war, and served in the East End of London during the Blitz. He and Kathleen Rogers married in Hammersmith in 1938, and at some point before 1951 he anglicised his first name to Basil. Shortly after Helen's birth, her father left the orchestra and returned to driving a cab to support the family. He later worked as a driving-test examiner, then became a civil servant with the Ministry of Transport. In 1951, he changed the family name to Mirren by deed poll. Mirren considers her upbringing to have been "very anti-monarchist". She was the second of three children; she has an older sister Katherine ("Kate"; born 1942) and had a younger brother Peter Basil (1947–2002). Her paternal cousin was Tania Mallet, a model and Bond girl. Mirren was brought up in Leigh-on-Sea, Essex.
Mirren attended Hamlet Court primary school in Westcliff-on-Sea, where she had the lead role in a school production of Hansel and Gretel, and St Bernard's High School for Girls in Southend-on-Sea, where she also acted in school productions. She subsequently attended a teaching college, the New College of Speech and Drama in London, "housed within Anna Pavlova's old home, Ivy House" on North End Road in Golders Green. At the age of eighteen, she passed the audition for the National Youth Theatre (NYT); and at twenty, she played Cleopatra in the NYT production of Antony and Cleopatra at the Old Vic, a role which she says "launched my career" and led to her signing with agent Albert Parker.
