| Catherine I was the wife of Peter the Great of Russia. She was born Martha Skavronskaya in 1684 in Lithuania, and orphaned while still an infant. A Lutheran pastor, Ernst Gluck, took her in and raised her as sort of a servant for his family; she was not taught to read or write. At the age of 18, at the beginning of the Great Northern War, she was betrothed (some accounts say briefly married) to a Swedish soldier who left when his regiment was evacuated after some Russian advances into the area.
Gluck and family were taken prisoners of the Russian general Sheremtev, and though Pastor Gluck was sent to Moscow as a translator, Martha became a servant in Sheremtev's traveling household. She converted to the Orthodox Church and was baptized with the new name of Catherine (Ekaterina). And she caught the eye of the Tsar's close friend Alexander Menshikov, himself risen from lowly origins. Some accounts say she became his mistress, but this seems unlikely since Menshikov was courting noble lady Darya Arnseneeva, who became a close friend to Catherine.
In the fall of 1703, Peter the Great noticed Catherine at his friend's house. He had hated his first wife, and his longterm relationship with an earlier mistress, Anna Mons, was falling apart at the time, so there was no obstacle to getting involved with Catherine. She and Darya accompanied Peter and Menshikov throughout Russia. Menshikov married Darya in 1706; Peter hesitated about marrying Catherine while his first wife still lived (in a convent) but did so privately in 1707, after the couple had three children already. The marriage was kept secret from even some of the highest government officials.
In February 1712, Peter married Catherine in public (after she had been re-baptized into the Orthodox Church). The two seemed to be a good match; she could calm Peter's seizures like no one else and was apparently always in a good mood when Peter needed cheering up. Unlike Peter, Catherine had a taste for pomp, and he built her several residences much fancier than he would have chosen on his own. They had 12 children, only two of whom reached adulthood.
Catherine remained aware of her origins; she was very different from the sheltered aristocratic women of Russia at the time. She remained deferential and polite to nobles and other countries' royalty so that no one could say she had become snobbish. Nonetheless, many Russian nobles did not approve of her. Peter had her crowned before he died, making it pretty clear that he considered her of royal rank and meant for her to rule after him. When he died in 1725, his own favorites who had gained power on merit rather than rank supported her, but much of the nobility thought Peter's grandson, descended from Peter's first wife, should rule, even though he was only nine.
The support (and money distributed to) the Guards, the most important regiments of Peter's army, ensured that Catherine had enough support to stay in power. Catherine tried to continue Peter's Westernizing policies while lightening the tax burden on the Russian people. Menshikov was her main advisor and probably the most powerful man in Russia, but Catherine occasionally went against him. She married her daughter Anna to Charles Frederick of Holstein over his objections and put Charles Frederick on her ruling council.
In the winter 1726-1727, Catherine caught a series of chills and fevers due to time outside during floods of the Neva River in St. Petersburg and before she had recovered, reviewing troops outside for hours. She died in March 1727 after two months of illness, having been persuaded by Menshikov to name her step-grandson, Peter's grandson Peter II, as her heir.
Sources: Robert K. Massie's Peter the Great: His Life and World and those listed under Monarchs of Russia. | 
