He is ʻUthmān bin ʻAffān bin Abil-ʻĀṣ bin Umayyah bin ʻAbd-Shams bin ʻAbd-Manāf bin Qusay bin Kilāb bin Mirrah bin Kaʻab bin Luʼay bin Ghālib (May Allah be well pleased with him).
Some facts about him:
Kunyas: Abu ʻAbdillāh, Abu ʻAmr, Dhu al-Nurayn [dhun-nurayn]. He is mostly famous by the latter.
Caliph ʻUthmān bin ʻAffān {May Allah be well pleased with him} was so beautiful and modest that he was allowed to marry two of the Prophet Muḥammad’s daughters {Peace be upon them}. ‘Abdullāh bin Ḥazm said:
“I saw ʻUthmān, and I never saw a man or woman more beautiful than him.”
—Siyar Aʻlām al-Nubalāʼ
No one else in the history of the world has married two daughters of a Prophet. This is the reason for his kunya Dhu al-Nurayn (“the possessor of two lights”).
Caliph ʻUthmān was also the first to emigrate/make Hijrah in the way of Allah to Abyssinia/al-Ḥabasha.
May Allah be well pleased with him.