Helena of Moscow
daughter of Ivan III the Great, Grand Prince of Moscow, and an uncrowned Grand Duchess of Lithuania and Queen of Poland as she would not convert from Eastern Orthodoxy to Catholicism.
Her childless marriage to Grand Duke of Lithuania and later King of Poland Alexander Jagiellon was a constant source of tension between the Grand Duchy of Moscow and the Grand Duchy of Lithuania. Instead of guaranteeing peace, Helena's marriage gave her father Ivan III an excuse to interfere in Lithuanian affairs accusing Alexander of mistreating Helena and repressing Orthodox believers. This became the pretext to renew the Muscovite–Lithuanian War in 1500. The war ended with a six-year truce in 1503; the Grand Duchy of Lithuania lost about a third of its territory. Despite political tensions and religious differences, the marriage was a loving one and the royal couple was close. After her husband's death in 1506, Helena wanted to return to Moscow but was not allowed. When she planned to run away, she was arrested and reportedly poisoned