- Han Solo: "Something's interfering with the hyperspace lane. I'm reading numerous mass shadows."
- Mahjo Reeloo: "Mass shadows?"
- Hondo Ohnaka: "Supermassive objects in realspace such as suns, enormous planets, things like that. They distort hyperspace. The gravity of these large objects creates these 'mass shadows,' which can be very dangerous."
- ―Han Solo, Mahjo Reeloo, and Hondo Ohnaka[src]
In hyperspace, a mass shadow was the gravitational signature of a large object in normal space. Since those shadows were potentially lethal to any starship traveling too near, it was necessary to avoid colliding with them by plotting precisely calculated hyperspace jumps. By simulating the gravity shadow of a celestial body, a ship's travel through hyperspace could be halted or their jump to hyperspace rendered impossible within an interdiction field.
During the High Republic Era, the Great Disaster began when the freighter Legacy Run encountered an unexpected mass shadow in the middle of a hyperspace lane. Although the freighter's captain, Hedda Casset, attempted to pilot the Run out of the way with only seconds to go before impact, the ship struck the obstruction at an oblique angle and tore itself apart.
During the Imperial Era, the main star of the Throffdon system went supernova and formed mass shadows. As smuggler Han Solo was en route to Gwongdeen, his ship, the Millennium Falcon, was pulled from hyperspace by the Throffdon star's mass shadows. The Galactic Empire was rumored to have developed a superweapon called the Mass Shadow Generator, which could exist in space and hyperspace simultaneously.
- The High Republic: Light of the Jedi
- Thrawn: Treason (Mentioned only)
- Pirate's Price
- Heir to the Jedi (First appearance)