Spartan-III Alpha company was the first of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2531, after being recruited as children orphaned by the war. Alpha Company, like all Spartan-III companies, were trained on the planet Onyx, which lasted for five years until they received their augmentations in November 2536. The Spartan-III program was run by former Spartan-II Kurt-051, and Senior Chief Petty Officer Franklin Mendez. Spartan-IIIs were known for being a cheaper version of the Spartan-II program, which included wearing Semi-Powered Infiltration (SPI) armor instead of the MJOLNIR that Spartan-IIs wore.
Notable Spartans of Alpha Company were Carter-A259, Emile-A239, and Jun-A266. All Alpha Company members, which the exception of those in Noble Team and any placed in Headhunter teams, were killed during Operation: PROMETHEUS in 2537.
These events are depicted in the novel Halo: Ghosts of Onyx.