Who is the Companion known as the Sayyid of the Ansar?

The Ansar had many chiefs, and the most famous of those among the Companions who were given this title were Sa'd ibn Mu'adh, Sa'd ibn 'Ubadah, Ubayy ibn Ka'b, and Al-Bara' ibn Ma'rur. The Prophet, peace and blessings be upon him, described them as such, and the most famous among them in this regard was Sa'd ibn 'Ubadah.