Côte d'Azur was a coastal city that was the main population center of Sigma Octanus IV, a UNSC colony world in FLEETCOM Sector Three. The population of Côte D'Azur was estimated to be 300,000, nearly all of whom were killed during the Battle of Sigma Octanus IV.
Côte d'Azur's citizens grew rice paddies outside of the city. The main sections on the latter interior of Côte d'Azur were the wharf and bay areas, the residential section, the downtown, and the docks. Côte d'Azur had a sewer system under the city. The sewer systems had steel pipes running along the top of the plastic conduits. The sewer systems had a two meter diameter pipe, with a steel grate, on the beach side near the edge of the city. The inhabitants used sodium vapor lamps, which washed everything above with an eerie glow.
In the year 2552, the Covenant launched a small attack against the Sigma Octanus system in hopes to retrieve a Forerunner artifact that was on display at the Côte d'Azur Museum of Natural History on Sigma Octanus IV's surface. When the Covenant invaded Côte d'Azur, they killed the entire population, save for twenty civilians (some of whom were wounded) who hid in a cargo ship. It is assumed that these twenty are the only to have survived.
The Covenant were in the process of securing the artifact and relaying messages to the ships above when the SPARTAN-II Blue Team entered the city. Blue Team managed to retrieve the artifact, save the remaining civilians, and escape back to their Pelican Dropship. Upon entering the Pelican and exiting the atmosphere, John-117 detonated a HAVOK Nuclear Warhead underneath the city streets, which destroyed the city and prevented the Covenant from finding anything else of value. Sigma Octanus IV and the remnants of Côte d'Azur still remain under human control.
- The city was probably named after the real Côte d'Azur, a region in the south-east of France.
- "Cote d'Azur" is French for "blue coast" and is the French name for the French Riviera.
- This was apparently the first contact that Blue Team had with Hunters, as they had to improvise to defeat them. After their armor-piercing bullets had no effect, John ordered the Spartans to switch to shredder rounds and shoot out the floor that the Hunters were standing on, dropping them to the floor below and allowing Blue Team to escape with the Forerunner artifact.