|Title|| Lord of Casterly Rock|
Warden of the West
Lord of the Westerlands
|Allegiance|| House Lannister|
|Died||In 130 AC, at Battle at the Red Fork|
|Spouse||Lady Johanna Westerling|
|Book(s)|| The Rogue Prince (Mentioned)|
The Princess and the Queen (Mentioned)
The World of Ice and Fire (Mentioned)
- For the Jason Lannister who was the father-in-law of Tywin Lannister, see Jason Lannister (son of Gerold).
During the civil war known as the Dance of the Dragons (129 AC-131 AC) Jason was loyal to King Aegon II and the greens against Rhaenyra's claim. Jason was killed by Pate of Longleaf in the Battle at the Red Fork, however, which left Casterly Rock in considerable disarray. Lord Jason's brother, Tyland, was the master of coin during the Dance of the Dragons.