The flagship of the UNSC Navy and the first Infinity-class supercarrier ever constructed, the UNSC Infinity is the largest single human warship ever constructed, with a crew of over 17,000. Construction on the Infinity began in 2544, and was initially complete and ready for duty just after the Human-Covenant War in 2553. The ship was initially a project of the Office of Naval Intelligence and was designed to act as an ark ship in the case of the total loss of all human colonies, but the budget for the ship became so large, the UNSC Fleet took partial ownership of the project. To ensure total secrecy, the Infinity was constructed in the Oort cloud of the Sol system, over a light-year from Earth.
These events are referenced in the novel Halo: Thursday War.