- "I just made the Kessel Run in twelve parsecs."
"[Chewbacca corrects him]"
"Not if you round down, buddy."
- ―Han Solo and Chewbacca on Savareen
The Kessel Run was a 20-parsec hyperspace route within the Akkadese Maelstrom used by smugglers and unscrupulous freighter captains to move spice from the spice mines of Kessel at the behest of the Pyke Syndicate, who relied on the foolhardy Kessel Runs to deliver the illicit substance to their customers. Han Solo, piloting the Millennium Falcon, made the infamous run in slightly over 12 parsecs, boasting about his ship's ability to endure shorter but more hazardous routes through hyperspace. By doing so, Solo broke a long-held record.
Astrid Fenris speculated that Solo had flown the freighter between two black holes in the Maw Cluster, and therefore the credit for the run should go to the gambler Lando Calrissian, who owned the ship at the time and so had been responsible for any modifications that allowed it to survive the pull of the black holes. Peko-Peko Munzati and a few other pilots speculated that the route Solo used to achieve this feat was an ancient purrgil migration route.
Behind the scenes
In a commentary track on the Star Wars Blu-ray release, George Lucas stated that ships in the Star Wars universe can't travel in straight lines while in hyperspace due to collisions with celestial objects. Thus, distance is an important factor in how quickly a ship can get from point A to point B. The Millennium Falcon's superior navigation computer allowed it to travel shorter distances between points and arrive faster.
Canon sources conflict on the veracity of Solo's claim of the Millennium Falcon making the Kessel Run in less than 12 parsecs. A New Hope: The Princess, the Scoundrel, and the Farm Boy describes the claim as a "lie" that the inexperienced Luke Skywalker is impressed with, but which the seasoned Obi-Wan Kenobi recognizes as nothing more than a boast. Return of the Jedi: Beware the Power of the Dark Side!, however, states in its narration that "Not every ship is created equal and the rebels have the ship that did the Kessel run in less than twelve parsecs." Solo: A Star Wars Story describes Han's Kessel Run as being slightly longer than twelve parsecs, while other ships tend to take at least twenty.