The RX-0 Unicorn Gundam 03 Phenex (aka Phenex) is a mobile suit introduced in Mobile Suit Gundam UC: One of Seventy Two. It also appears in the manga Mobile Suit Gundam U.C. 0096: Last Sun and the Mobile Suit Gundam Unicorn novel. It makes its animated debut in the movie Mobile Suit Gundam Narrative, which succeeds the events of the Mobile Suit Gundam Unicorn OVA, and is piloted by Rita Bernal.

The RX-0 Unicorn Gundam 03 Phenex was a new machine secretly built under the direction of a EFSF official who disapproved of the Vist Foundation's involvement in the UC Project. Using a psycho-frame body delivered in advance, it was assembled independently by the Earth Federation Forces and reflects the data of Units 1 and 2. Rather than that of a Unicorn, the Phenex's motif is that of a phoenix, illustrated with a much more elaborate horn/V-fin and a golden body.