The colony world of Arcadia, one of the many outer worlds to be colonized in the 25th century, was settled sometime in 2429.

The Battle for Arcadia was a battle for the colony Arcadia in the Procyon system, which occurred in the immediate aftermath of the Harvest Campaign.

The Fall of Arcadia, also known as the Second Fall of Arcadia, was a Covenant invasion and subsequent loss of the colony world of Arcadia in the Procyon system on September 9th 2549.