|Appearance(s):||GTA: State of New Kellen|
|Also known as:||Stans
|Home:||Grove Aldeway, Levanda City, New Kellen|
|Family:||Blake Matheson (son)
Johnathan Matheson (son)
Samuel Matheson (son)
Kate Matheson (daughter-in-law)
Ivan Matheson (grandson)
Jack Matheson (grandson)
|Main affiliation:||Matheson Crime Family (leader)|
|Vehicle(s):||Armored Sultan Sedan
Stretch Limousine (stolen)
|Businesses:||Every businesses and properties owned by the Matheson Mafia|
- "Look, there's no good people or bad people in this world. It's just the decision made by everybody. I chose this path and there's no way for me to turn back and correct myself. And it isn't my fault for being a mobster, I killed many people already just for the good of my family, and my mafia. Sometimes I kill the bad and good people, sometimes I just let them live. "
- ―Stanley Matheson
Stanley Matheson is described in the LCPD dossier as "intelligent and extremely powerful." He is fiercely loyal to his own gang and his neighborhood, and as the leader and don of his Matheson Mafia, he uses them as a means to keep his businesses and his family's influence in the city. Among his allies and his own gang, he is respectful and is against discrimination, and like the previous leaders of the mafia, he allows members who are non-white Americans to become a high-ranked member of the mafia, as he believes that it could keep the mafia united and powerful, which actually works.
Apart from that, Stanley is apparently short-tempered, as he is easily angered and quick to resort to violence. He does not hesitate to order his fellow gang members like Jack to assassinate other gang members of the hostile criminal organisations. He is also extremely angry when his son, Blake, who used to be a respectful and high-ranked member of the mafia, revealed himself to be a secret government agent and betrayed them to the FIB. However, Stanley often shows his sensitive side with other characters like Jack and Johnathan as well as viewing one of his gang members, Huang Lee Xuan as a son figure due to his loyalty and his contribution to the mafia.
Stanley is also intelligent. He is a skilled hacker as in the mission Make Them Pay, he is able to hack his clients' Lifeinvader accounts who owe him protection money in order to track their current locations so that Jack could track them down and collect their money. Stanley also admits that when he was younger, he used to be a drug addict and usually abused cocaine when he was free in his home. As he grows older, he decided to quit and manages to become clean from drugs again, and also, in the mission Get Those Drug For Me, when Park Jae-sok tries to give him some cocaine for him to abuse them, he refused and said, "Nah, I've quit."
Despite being aggressive and remorseless, Stanley does show a feeling towards his family and his gang as well as his allies. Especially helping Jack to rescue his girlfriend by sending him backups. Also, after Jack dates Jessica for the third times, Stanley will phone Jack, saying that he has send his men to watch over their date as well as telling Jack that he has been suspicious toward Jessica's strange behavior, believing her to be a secret government agent like his son, Blake. He is also a generous figure, as Park mentions that a year ago, he helped to donate a million dollars to the charity in order to help the people who are living in poverty in Africa.