Ian Gallagher (born 11 March 1989) is the third oldest Gallagher sibling and is aged 15 at the beginning of the first series in 2004. He is the son of Monica and Gary Bennett, revealed when his blood group was found to be incompatible with the rest of his siblings'. His half-brothers are Phillip Gallagher, Carl Gallagher, Liam Gallagher and Sean Bennett, and his half-sisters are Fiona Gallagher, Debbie Gallagher, and Stella Gallagher. He has one niece, Katie Maguire, and works as a barman at The Jockey.
Ian is gay, having various relationships with usually older men throughout the run of the programme. Kash Karib is to date his only long-term boyfriend, though he has a brief relationship with Sean Bennett, and an ongoing friendship with Mickey Maguire. He also has sex with one girl (which does not affect his sexuality), and a relationship of convenience with Mandy Maguire, to protect his secret. Because he is unaware of his parentage at the time, Ian also unknowingly sleeps with his half-brother. Ian sees Sean at their biological father's funeral and later tells the truth to Sean, who wants to keep seeing Ian, but eventually agrees that they can not ignore their familial relationship.
In the early series, Ian is depicted as closest to his brother Phillip, with whom he shares a room, and is initially the only member of his family to know that he was gay. The brothers often have to look out for each other more than any of the other characters, due to being party to each others' secrets. In later series, all the family, even Frank, are aware of his sexuality.
Ian leaves in the first episode of the 6th series after suffering amnesia. He is seen in episode two in a clip of him partying abroad and appears on webcam in later episodes. He returns in the seventh episode; this features the debut of Danny, a deaf teenager whom Ian unwittingly transports back to the in the trunk of his car. Ian now lives in the house of Danny's deceased grandfather, which was leased to him by Danny's Aunt Pegg, in gratitude for looking after him. Danny and Pegg later move to .