The Battle of Procyon V was a battle which took place in the 26th century of an alternate timeline. It was the final battle in a war between the United Federation of Planets and the Sphere Builders. The USS Enterprise-J led the Starfleet forces in the battle. (ENT episode: "Azati Prime")
The battle also played a pivotal moment in the Temporal Cold War as it was revealed that next to the Sphere Builders, the Na'kuhl, the Vorgons, an individual known as the Envoy, and admiral Leeta of a restored Terran Empire in the mirror universe also played roles in it, together forming an organization called the Temporal Liberation Front that advocated that time travel should not be restricted or prevented.