A star system in the alternate reality where most of Starfleet's ships were occupied in 2258, leaving cadets to crew the vessels sent to answer Vulcan's distress call.
The Laurentian system is mentioned in the 2009 film Star Trek, set in the alternate reality created by Nero's arrival. When Vulcan sends a distress call in 2258, the bulk of Starfleet's fleet is engaged in the Laurentian system and cannot respond.
Starfleet therefore fills the ships docked at Earth with Academy cadets, which is how James T. Kirk, Uhura, McCoy, Sulu and Chekov come to be aboard the newly completed USS Enterprise on its first mission.
After Vulcan is destroyed, acting captain Spock decides to rejoin the fleet in the Laurentian system instead of pursuing the Narada to Earth. Kirk argues fiercely against the plan and is put off the ship on Delta Vega, an act that sets up his meeting with the older Spock.