December 23, 1777 - December 1?, 1825: Age 47?
Alexander was the grandson of Catherine the Great (see November 17). She had no faith in his father, her son Paul, so she took Alexander from him soon after he was born. His childhood was characterized by the battle between his grandmother and his father and, like certain children under such circumstances, he withdrew into himself, presenting to the outside world whatever personality and views seemed to suit whomever he was dealing with.
Catherine died in 1796. Paul I succeeded her and tried to put through a number of reforms that were met with hostility and conflict. He was murdered in 1801, less than five years after his ascension, and Alexander became Tsar at the age of 23. It seems likely that Alexander knew of the plots against his father, but it is not known whether he was actually implicated in his father's murder.
His reign was difficult. The balance of power in Europe was constantly shifting, and in 1812 he had to deal with the invasion of Napoleon. Reform was desperately needed, but bitterly opposed by many factions. He tried to put through many of the same kinds of reforms his father did, but gradually, as he became older, he began to reverse them, and became suspicious of the people around him. It was not unfounded; at least one attempt was made to kidnap him. In the autumn of 1825 he became ill while traveling and died of typhus on December 1. His wife died a few months later.
His death came as a great surprise. There was confusion around the succession, as he had no living legitimate children. His brother Constantine had renounced the succession some years earlier but that had not been announced publicly. In the end, another younger brother, Nicholas, succeeded him as Nicholas I.
There were rumours that he had really faked his death and funeral, and that he was living incognito as a monk or in some foreign land. A hermit named Feodor Kuzmich emerged, travelling around Russia doing good works for people, and speaking and acting in a mysteriously aristocratic fashion. Many people, even today, believe that Feodor Kuzmich was in fact Alexander I, who had chosen this strange way to renounce his throne and expiate the sin of patricide. People believed that an unknown soldier had been buried in Alexander's place. So persistent was this rumour that the Soviets opened his tomb in 1925, 100 years after his death. Inside they found nothing. The tomb was empty. Nobody knows why.
Sources: Wikipedia, Imperial Legend