This is a list of all missions in Grand Theft Auto III, sorted by type, island and mission-giver. There are 51 storyline missions, 17 phone missions, 4 Off-road Missions and 4 Remote Controlled Missions.
Claude is betrayed by his girlfriend Catalina when she shoots him during a bank heist, leaving him for dead. He survives and is arrested, but on the way to the penitentiary, the Colombian Cartel ambushes the convoy to kidnap another prisoner, destroying the bridge in the process and isolating the island of Portland from other parts of Liberty City, and he and another prisoner named 8-Ball manage to escape. With his new allies, he eventually forms a connection with the Leone family by destroying the neighboring Triads and Forelli family. He finds out that Catalina has become a co-leader of the Colombian Cartel, and eventually destroys their ship filled with the drug SPANK. However, Salvatore Leone has grown paranoid and no longer trusts easily, so when Maria lies and says that she and Claude are having an affair just to spite him, he sends Claude to his death by planting a bomb in a car he ordered Claude to take away. Maria finds out and warns Claude just in time and, along with Yakuza leader Asuka Kasen, they leave Portland on a boat to Staunton Island.
- Introduction: Cutscenes depicting Catalina's betrayal of Claude, and the explosion which leaves Portland isolated from the rest of the city and Claude's escape with 8-Ball.
- Luigi's Girls: Drive to the hospital and bring Misty to Luigi's club.
- Don't Spank Ma Bitch Up: Kill a drug dealer and steal, respray and deliver his car to Luigi.
- Drive Misty For Me: Pick up Misty from Hepburn Heights and drive her to Joey's garage.
- Pump-Action Pimp: Kill two pimps.
- The Fuzz Ball: Bring as many prostitutes as possible to the Old School Hall.
- Mike Lips Last Lunch: Steal and arm Mike Forelli's car with a bomb and blow him up.
- Farewell 'Chunky' Lee Chong: Kill Lee Chong.
- Van Heist: Damage and steal a Securicar and bring it to a garage in Portland Harbor.
- Cipriani's Chauffeur: Drive Toni Cipriani to the Laundry and to his home.
- Dead Skunk in the Trunk: Bring a car to the car crusher.
- The Getaway: Pick up and drive three mafia members for a bank robbery and bring them back to their hideout.
- Taking Out The Laundry: Destroy three laundry vans.
- The Pick-Up: Pick up a briefcase, waste the Triads and take it to the Cipriani Restaurant.
- Salvatore's Called A Meeting: Pick up and bring Joey, Luigi and Toni to Salvatore Leone's mansion.
- Chaperone: Drive Maria to Chico and a party in Atlantic Quays before driving her back to Salvatore's mansion.
- Triads and Tribulations: Kill three triad warlords.
- Blow Fish: Drive a Truck to the Triad's fish factory, before blowing up the factory.
- Last Requests: Meet Maria and Asuka at Callahan Point, before escaping from Portland with them. Unlocks Staunton Island.
Claude is now a rogue from the gangs in Portland, with the Leone Family and the Triads after him, and begins making a new connection in the Yakuza. He assassinates Salvatore to prove he is no longer working for him, and he is introduced to Asuka's powerful brother Kenji and a corrupt policeman named Ray who helps him in exchange for doing his dirty work. Ray introduces him to Donald Love, a billionaire real estate mogul, who Claude helps as well for the benefit of Love and his company. However, to start a gang war and lower the real estate price of land Love wants, he steals a Colombian Cartel vehicle and kills Kenji, igniting a war between the two. He eventually finds Catalina again, who kidnaps Maria, kills Miguel and Asuka, and ransoms Maria for $500,000.
- Sayonara Salvatore: Kill Salvatore Leone.
- Under Surveillance: Kill the spies located around Staunton Island.
- Paparazzi Purge: Kill a reporter using a boat.
- Payday For Ray: Go to four payphones located around Staunton Island before bringing Ray's money to him.
- Two-Faced Tanner: Head to the casino and kill Tanner.
- Kanbu Bust-out: Destroy a cell wall in the police station, and drive a high ranked Yakuza member to the Yazuka Dojo
- Grand Theft Auto: Bring three sport cars to a garage.
- Deal Steal: Pick up a contract and ambush a deal between the Cartel and the Yardies, before stealing and taking the money to the casino.
- Shima: Collect two briefcases of protection money, and kill the Diablos, before collecting the third briefcase and delivering the briefcases to the casino.
- Smack Down: Kill as many yardie drug dealers as possible.
- Silence The Sneak: Torch Leon McAffrey's house and kill him.
- Arms Shortage: Go to Phil Cassidy's base and defend him from the Colombian Cartel.
- Evidence Dash: Ram a vehicle and pick up six images before torching the car that the pictures are in.
- Gone Fishing: Kill Ray's partner using a boat.
- Plaster Blaster: Ram the Ambulance and kill Leon McAffrey again, who is still alive.
- Liberator: Go to the Cartel Compound before rescuing the Old Oriental Gentleman and bring him back to Donald's building.
- Waka-Gashira Wipeout!: Kill Kenji Kasen in a Colombian car and dump the car.
- A Drop In The Ocean: Pick up six packages using a boat and bring it back to Donald's building. Unlocks Shoreside Vale.
- Grand Theft Aero: Go to the airport, kill the Colombians, get the packages at the construction site, and bring them back to Donald's building.
- Escort Service: Defend a Securicar.
- Decoy: Get inside a Securicar and act as a decoy around for three minutes.
- Love's Disappearance: Donald Love is not at the building as usual, so the decision is to leave the Love Media building.
- Marked Man: Take Ray to the airport and then go to his lock-up.
- Bait: Lead three Colombian death squads into a trap.
- Espresso-2-Go!: Destroy nine espresso stands.
- S.A.M.: Blow up a Dodo with a rocket launcher and bring the SPANK packages to Asuka.
- Ransom: Asuka and Miguel are killed, Maria is kidnapped by Catalina, and there is a letter left by her.
- Turismo: Win a street race.
- I Scream, You Scream: Arm an ice cream truck with a bomb and blow up a group of gang members.
- Trial By Fire: Burn twenty-five Triads in two minutes.
- Big 'N Veiny: Pick up some magazines and take them to XXXMags in Red Light District.
- The Crook: Bring a bank manager to the dog food factory and crush the evidence.
- The Thieves: Bring two thieves to the food factory and respray Marty's car.
- The Wife: Bring Marty's wife to the food factory and and dump the car into the sea.
- Her Lover: Bring Carl to the food factory.
- Bling-Bling Scramble: Win a checkpoint race.
- Uzi Rider: Kill ten Diablo gang members.
- Gangcar Round-Up: Bring three gang cars to a garage in Newport.
- Kingdom Come: Destroy some SPANKed up madmen vans and reveal the betrayal of King Courtney.
- Uzi Money: Drive-by 25 Purple Nines in two minutes.
- Toyminator: Destroy three gang cars with an RC Bandit.
- Rigged to Blow: Bring an armed car to a garage before it explodes.
- Bullion Run: Pick up as many pieces of bullion as possible and take them to a garage.
- Rumble: Kill all remaining Purple Nines in a final battle using only baseball bats.
- Patriot Playground: Pass through fifteen checkpoints at the Portland Beach.
- A Ride in the Park: Pass through twelve checkpoints in the park.
- Multistorey Mayhem: Pass through fifteen checkpoints in the multistorey car park.
- Gripped!: Pass through twenty checkpoints in Cedar Grove.
Remote controlled vehicle missions
- Diablo Destruction: Destroy as many Diablo Stallions as possible with an RC car.
- Mafia Massacre: Destroy as many Mafia Sentinels as possible with an RC car.
- Casino Calamity: Destroy as many Yakuza Stingers as possible with an RC car.
- Rumpo Rampage: Destroy as many Hoods Rumpo XLs as possible with an RC car.
- Import/Export: Collect several different vehicles in both Portland Island and Shoreside Vale. Two missions in Portland and one in Shoreside Vale.