Cortana (Earth-2042)

"I know what you're thinking, and it's crazy. Unfortunately for us both ... I like crazy."

- Cortana to John-117

Cortana (serial number: CTN 0452-9) was an "smart" AI in service with the Systems Alliance Space Command and the Galactic Republic. Unique and exceptionally intelligent even among smart AIs, she was one of the most important figures in the Clone Wars, and served as John-117's partner in the final months of the Republic. Her flexibility and tactical skill proved invaluable in boosting the combat ability of the Halcyon-class light cruiser Pillar of Autumn, the orbital defense platform Cairo Station and the Stalwart-class light frigate In Amber Clad. In addition, she held vital data pertaining to the Halo Array, including the activation index from Installation 04.

Source

 * https://www.halopedia.org/Cortana