Riley O'Connor is a scientist and one of the three possible characters to choose from in Doom II RPG.
Riley is sent with a group of marines to the facilities of UAC on the Moon where there was an invasion of creatures from Hell. He was not a planned member of the expedition. In order to quickly reach the Moon, a ship of the rookie scientist Riley O'Connor was commandeered by the Marines. Riley accompanies the commander Kira Morgan and Sergeant Stan Blazkowicz to discover the origin of the invasion and stop on time.
Depending on which character you choose, the other two come with Caldex to participate in their own way through the base.