A clone trooper captain, also referred to as Clone Captain, was a rank attained by certain clone trooper officers.
Within the Grand Army of the Galactic Republic, Clone Captains typically oversaw companies consisting of 144 troopers, though this wasn't universally true. The sixteen captains within a regiment reported to their Clone Commander, and when applicable, a Jedi General and Jedi Commander if their units included such leadership. Captains utilizing standard Phase I armor displayed four maroon circles on the left side of their chest plate, along with a maroon stripe running down each arm, vertically along the helmet's center, and horizontally around the visor. Clone Captains could also be assigned to forces in the Galactic Republic Navy. The position of Clone Captain remained in use during the initial stages of the Imperial Era as part of the Stormtrooper Corps.
Rex was a well-regarded and prominent Clone Captain who led both the 501st Legion and its Torrent Company. He frequently received direct orders from Jedi General Anakin Skywalker, acting as Skywalker's second in command. Rex also held authority over the Execute Battalion and the Carnivore Battalion within the 501st Legion.
Toward the end of the Clone Wars, Supreme Chancellor Sheev Palpatine commanded Clone Captains, along with the rest of the Grand Army, to betray and kill their Jedi superiors. Among these was Clone Captain Grey, who carried out the execution of Jedi General Depa Billaba on Kaller.
During the early years of Darth Sidious' rule as Galactic Emperor, the rank of Clone Captain persisted within the Imperial Military as the clones continued their service as the initial generation of stormtroopers. Howzer and Wilco were two notable troopers holding the Clone Captain rank in the Galactic Empire, though the former was later arrested for defying orders, and the latter was executed by the corrupt Vice Admiral Edmon Rampart for his refusal to submit a false military report.