Courtney Heironimus (コートニー・ヒエロニムス Kotoni Hieronimusu) is a ZAFT test pilot with high spatial awareness and prodigal sense of piloting. He was initially a civilian employee of Verne Design Bureau and worked as a test pilot in the development team. He works for ZAFT after Verne was merged with other companies to form Integrated Design Bureau.
Not much of Courtney's past is known prior to his working with ZAFT. One of the mobile suits that Courtney was known to have piloted during the First Alliance-PLANT War was the YMF-X000A Dreadnought Gundam. Thanks to his high spatial awareness, he was able to use the XM1 "Pristis" beam reamers that were controlled through the DRAGOON System and defeated Gai Murakumo, who was piloting a ZGMF-600 GuAIZ, during a mock battle. However, he never used the Dreadnought's back-mounted DRAGOON pods as ZAFT never produced the parts before the testing of Dreadnought ended.
After the end of the War, he was one of the test pilots for the ZGMF-X999A ZAKU Trial Type and encountered a large squadron of the Earth Alliance's GAT-02L2 Dagger Ls during a test run in the South American rainforest. The Dagger Ls were subsequently wiped out by Courtney after they attacked him, in violation of the treaty between ZAFT and the Earth Alliance that no fighting would occur in neutral zones. After this encounter, Courtney met freelance journalist Jess Rabble; after seeing Jess's ZGMF-X12 Gundam Astray Out Frame, he immediately suspected that it was the missing "Number 12", a reference to ZGMF-X12A Testament Gundam, and provided one of the first clue about Out Frame's origin.
Before the beginning of the second war, Courtney was the test pilot of the experimental XMF-P192P Proto-Chaos, and later, the ZGMF-X24S Chaos Gundam. When the Chaos was stolen, he launched in the Proto Chaos to fight against a separate group that attacked Armory One. He later served as a test pilot for ZGMF-X56S/θ Destiny Impulse Gundam and used Unit 03, at the Battle of Messiah. After the war, he left ZAFT and disappears.