Oerba Yun Fang of Final Fantasy XIII is a 21-year old l'Cie from Oerba on Gran Pulse who wakes from crystal stasis thirteen days prior to the start of Final Fantasy XIII along with Oerba Dia Vanille: this event perpetuates the branding of Serah Farron by the fal'Cie Anima, which in turn starts off the events of Final Fantasy XIII.
After she escapes from Anima's Vestage with Vanille, Fang begins serving as Cid Raines's subordinate in the Cavalry. She eventually meets Snow and becomes his partner as part of Cid's plan to overthrow the Sanctum. She later befriends Lightning. After rescuing Sazh and Vanille on board the Palamecia, she and Vanille reunite. Later, after being told about their focus and resolving to fulfill it even if she has to fight her friends, Fang has to fight and tame the Eidolon Bahamut. On Gran Pulse, despite Vanille's protests, Fang reveals that she was responsible for scarring Cocoon's shell centuries earlier and bringing deadly recriminations on the population of Gran Pulse.
When they face Orphan, despite the party's pleas for Fang to not transform into Ragnarok, Fang eventually transforms into an incomplete version and fights the fal'Cie alone, but gets tortured as a result of her failure, only to be saved by Lightning's group. After Orphan's destruction, Fang and Vanille complete their Focus by becoming Ragnarok to save Cocoon from crashing into Gran Pulse. In Final Fantasy XIII-2, Fang and Vanille appear to help Serah escape from the endless dream in the Void Beyond that Caius placed her in, and at the end they are rescued from Cocoon's pillar when it finally collapse. By the events of Lightning Returns, after awakening and seeing Vanille being used by the Order, Fang has taken up residence in the Dead Dunes and becomes the leader of a bandit group bent on thwarting the Order from obtaining a relic within the desert. She attempts to destroy the relic so Vanille can be saved from being killed by the ritual. Fang appears on the final day, helping Lightning dissuade Vanille from going through with the ritual and helps her guide the souls of the dead to the new world.
Fang was originally scripted to be a male character during the early stages of Final Fantasy XIII's development, but early in the writing stage, was rewritten as a female character. Along with this, the sex appeal that was originally going to be part of Lightning's look was transferred to Fang to give Lightning a more hard-edged persona. Fang is voiced by Rachel Robinson in English, and Mabuki Andou in Japanese.