The X-EX01 Gundam Calibarn (X-EX01 ガンダムキャリバーン X-EX01 Gandamu Kyaribān?) is a mobile suit introduced in Mobile Suit Gundam the Witch from Mercury. It is used by the Suletta Mercury near the finale of Season 2.

The Vanadis Institute developed countless prototype units in addition to the Lfrith before the establishment of GUND FORMAT technology. Of these units, the Calibarn took the most strikingly different direction from that of the Lfrith. Unlike the Lfrith, which could be operated with minimal impact on the human body within a certain Permet Score, Calibarn prioritized mobile suit performance to seek the utmost limits of GUND-ARM capabilities and adopted extreme measures that did not guarantee the pilot's life protection at all. After losing to the Lfrith in the development competition, it is said that all records of the Calibarn were destroyed, and it was made off-limits and sealed away. Although it aimed to become the mainstream of GUND-ARMS, the Calibarn could very well have been considered the most cursed of all Gundams from the public sentiments.