- "Catch you later, homeboys."
- — Eddie Pulaski.
- — Ryder.
Catalyst is a mission in Grand Theft Auto: San Andreas, given to protagonist Carl Johnson by fellow Grove Street Families member Ryder from his home in the Grove Street cul-de-sac in the Ganton district of Los Santos, San Andreas.
Carl pays another visit to Ryder, who is making his own "water" (marijuana dipped in embalming fluid and then laced with PCP) after he couldn't find it in his backyard. While Carl and Ryder are talking, Tenpenny and his accomplices drop by to inform the two that there will be a army munitions train passing through town shortly, and that enemy gangs such as the Ballas will try to raid the train.
The two immediately depart, arriving at the train only to find the Los Santos Vagos have ambushed the train first and are attempting to offload munitions fighting the Grove Street boys. Once the Vagos are dead, the Ballas show up and try to take the train. Not wanting to lose the munitions, Carl jumps on the train. Ryder is now in the back of his Picador, who waits with a GSF member driving behind the train, with Carl throwing some boxes to him. After acquiring sufficient munitions, the two are pursued by the police. They go to the nearby Pay 'n' Spray to lose the cops, and drive back to Ryder's home.
In order to complete the mission the player must:
- Drive Ryder's truck to the ammo train
- Shoot the Vagos robbing the train
- Protect the train from the Ballas
- Climb onto the back of the train
- Toss the munitions boxes to Ryder
- Use the nearby pay 'n' spray to lose the cops
- Take the crates back to Grove Street
- According to this mission, Tenpenny has a drug addicted wife.
- The Song heard in the pre-mission cut scene is Fantastic Voyage by Lakeside, this song can also be heard on Bounce FM.
- When Tenpenny and Pulaski enter the kitchen no one is behind them, then the next second, Hernandez is behind them.
- Also during the cutscene CJ disappears for a few seconds, and reappears again, when Tenpenny informs him and Ryder about the ammo train.