Her Imperial Highness Grand Duchess Olga Konstantinovna of Russia (in Russian Великая Герцогиня Ольга Константиновна) (3 September 1851 - June 18 1926) was the queen consort of King George I of Greece.
A granddaughter of Tsar Nicholas I of Russia and cousin of Tsar Nicholas II, Olga was the daughter of Grand Duke Konstantin Nikolaevich Romanov and Alexandra Iosifovna, a daughter of the Duke of Saxe-Altenberg. She met the young king during his trip to Russia to meet with his sister Dagmar, the Danish wife of Tsar Alexander III. They fell in love and married in 1867, when she was sixteen years old.
Together they had eight children:
- Constantine (1868-1923), who succeeded his father as king.
- George (1869-1957), High Commissioner of Crete.
- Alexandra (1870-1891), married Grand Duke Paul Alexandrovich of Russia (son of Alexander II of Russia). Mother of Dmitri Pavlovich Romanov, assassin of Grigori Rasputin.
- Nicholas (1872-1938)
- Mary (1876-1940), married first Grand Duke George Mikhailovich of Russia and second Perikles Ioannidis.
- Olga (1881, died when three months old)
- Andrew (1882-1944), father of Prince Philip, Duke of Edinburgh.
- Christopher (1888-1940), father of Prince Michael of Greece.