Uthman was born into the wealthy Umayyad clan of the Quraish tribe in Mecca, a few years after Muhammad. Unlike most of his kinsmen though, he was an early convert to Islam, and was well known for using his wealth to benefit charities. He was also married to two of Muhammad's daughters at seperate times, earning him the nickname Dhun Nurayn or the "Posessor of Two Lights". During the life of Muhammad, he was also part of the first Muslim emmigration to Abyssinia, and the later emmigration from Mecca to Medina.
According to Islamic tradition, Uthman was one of the ten people for whom it was witnessed that they were destined for Paradise; one of the six with whom Muhammad was pleased when he died. Uthman was also one of the first men to memorize the Quran and he would be instrumental to it's compilation after the death of Muhammad.
Uthman would become caliph after the assasination of Omar in 644. Prior to his death, Omar appointed a group of six men to choose his sucessor from among themselves. Included in this group were Uthman and Ali. The comittee chose Uthman.
He reigned for 12 years, and during his rule, all of Iran, most of North Africa, the Caucuses and Cyprus were added to the Islamic empire. In order to strengthen his control over the empire, Uthman appointed many of his kinsmen to governor positions, including Muawiyah I. This caused many problems though, and many people were angered by Uthmans preferrential treatment of his own kinsmen. This matter was not helped by the fact that some of the misrule by some of the governors he appointed, and was worstened by the involvement of some Umayyad's in a plot to kill the son of Abu Bakr.
The problem would grow so large that parties from Egypt and Iraq would convene in Medina to adress their grievances to Uthman directly. Eventually, the parties would grow impatient with Uthman and lay seige to his house for more than 20 days. Eventually, some members would break in, and assasinate both Uthman and his wife in 656. Despite the crowds outside his home, Uthman refused help from his old friends, and was reading the Quran when he was murdered. He is buried in Medina.