Elizabeth II

She took the throne on February 6, 1952 and has reigned over Great Britain for a remarkable 58 years and counting. (Equally impressive, she has been married to Prince Philip since 1947.) Just 25 when she first assumed the throne, Queen Elizabeth II is the mother of four children, with Charles, Prince of Wales, her designated heir. She has witnessed the royal family become entangled in some major controversies (notably after the death of Princess Diana in 1997), but maintained signficant popularity in Britain. Helen Mirren won the 2007 Best Actress Oscar for portraying her in "The Queen."