Derry Girls

• Saoirse-Monica Jackson as Erin Quinn, aged 16 at the start of the series. Erin is passionate and ambitious, but at times alternatively vain or overly concerned with how she is regarded by others. Her dark sense of humour and sarcastic nature often get her in trouble.
• Louisa Harland as Orla McCool, Erin's maternal cousin, aged 15 at the start of the series. Orla is very detached and eccentric, often assumed to be dim-witted by those around her. Unlike most of her friends, Orla does not care what anyone else thinks of her. She often amuses herself by invading Erin's privacy for fun.
• Nicola Coughlan as Clare Devlin, one of Erin's best friends. Clare often acts as the voice of reason in the gang, as she is far more intimidated by authority figures than her friends. At the end series one finale, Clare comes out to her friends and the school as a lesbian.
• Jamie-Lee O'Donnell as Michelle Mallon, one of Erin's best friends. Michelle is the wild child of the group, and her troublemaking tendencies often get her and her friends into trouble. She is shown to have a very keen interest in sex, drugs and alcohol, and shows almost no respect to any figures of authority, including her own mother.
• Dylan Llewellyn as James Maguire, Michelle's maternal cousin. English-born to an Irish mother, James is sent to live in Derry with his aunt Deirdre and cousin Michelle while his mother goes through a divorce. Due to his English accent, he is enrolled for his safety at an all-girls school. Adults and teens alike perceive James as effete and ineffectual, and just about everyone in Derry assumes he is gay, over his protestations.
• Tara Lynne O'Neill as Ma/Mary, Erin's disciplinarian mother and the matriarch of the Quinn/McCool family. She tolerates no attitude or trouble from her daughter, but is loving and usually only wants what is best for her family. She has been married to Gerry for 17 years at the start of the series.
• Kathy Kiera Clarke as Aunt Sarah, Orla's mother and Mary's sister. Sarah is caring but dim-witted, and often points out things that are painfully obvious. Although caring towards Orla, she is an inattentive mother and takes little responsibility for raising her. Like Orla, Sarah spends most of her time in Mary's house, where Mary does all the work, rather than their own house next door, which is sometimes mentioned but not shown.
• Siobhán McSweeney as Sister Michael, the headmistress of the school that the girls attend. She rules the school with an iron fist, and responds to most events with eye-rolling or sarcasm. Sister Michael seems to treat being a nun as a job rather than a calling, treating priests with indifference or even contempt and even joking that she became a nun for the free accommodation.
• Tommy Tiernan as Da/Gerry, Erin's father. Gerry is relaxed and very loyal and protective of his family. He is from the Republic of Ireland and holds an unspecified job where he drives 8 hours a day, and has a very strained relationship with his father-in-law.
• Ian McElhinney as Granda Joe, Mary and Sarah's father and Erin and Orla's grandfather. Joe moved in with the Quinns after his wife died. Although on good terms with the rest of the family, Joe shows nothing but contempt for Gerry, constantly criticising him and encouraging Mary to leave him.
• Leah O'Rourke as Jenny Joyce, the prefect of the girls' school and a suck-up. Jenny and the gang detest each other, and she often flaunts her wealth and position of power. Incredibly sanctimonious, the only person who can rein her in is Sister Michael, who is as contemptuous of her as she is the rest of the student body.

• Beccy Henderson as Aisling, Jenny's best friend and sidekick.
• Claire Rafferty as Miss Mooney, Sister Michael's deputy.
• Amelia Crowley as Deirdre Mallon, Michelle's mother and James' aunt, who is a nurse.
• Kevin McAleer as Uncle Colm, Joe's brother, whom the family consider incredibly dull and boring.
• Paul Mallon as Dennis, the aggressive proprietor of the corner shop which the girls frequent.
• Philippa Dunne as Geraldine Devlin, Clare's mother

A Derry Girls book was released on 12 November 2020, entitled Erin's Diary: An Official Derry Girls Book, published by Trapeze Books.[18]

Located at 18 Orchard Street in Derry,[21]  a mural of the main cast of characters can be seen on the side of Badger's Bar.[22]  This popular tourist attraction was created by UV Arts and is one of many political murals across the city. Derry is known for politically charged art, and the famed mural speaks to the popularity of the television programme and its relation to cultural change in the area. [23]

Derry Girls has received critical acclaim. On Rotten Tomatoes, the first series holds an approval rating of 100 per cent based on reviews from 24 critics. The website's critical consensus states: "A perfectly curated cast and raw writing drive Derry Girls's dark humor as creator Lisa McGee makes frenetic light of teen life in 1990s Northern Ireland".[24] The second series has an approval rating of 97 per cent, based on reviews from 30 critics. The website's critical consensus states that "The sophomore season of Derry Girls doesn't lose any of its irreverent charms thanks to its predictably unpredictable romps and canny characterizations".[25]

Derry Girls was the most watched series in Northern Ireland since modern records began in 2002, with an average audience of 519,000 viewers and a 64.2 per cent share of the audience.[26] Una Mullally of The Irish Times praised the series: "The writing in Derry Girls is sublime, the performances perfect, the casting is brilliant."[27] On 11 January 2018, after the first episode had aired, the programme was renewed for a second series.[28] Each episode was watched by over two million people.[29] At the conclusion of the first series, Barbara Ellen of The Guardian wrote that Derry Girls evoked such programmes as The Inbetweeners, Father Ted and Bad Education.[30]

As there are slight political undertones to the show, responses have highlighted the comedic nature as keeping the material lighthearted enough to enjoy. Certain writers from various online articles have noted that their own Northern Irish family appreciated the way the show gave an honest portrayal of how life was for teens in the Troubles, and how much was endured by families during that time.[31] The way it portrayed the events and circumstances with a sense of normalcy echoed the real lives of both Protestants and Catholics in that area.[31]

Lisa McGee based events in the programme on her own life, such as writing a letter to the Clintons' daughter, Chelsea.[32] Adding real stories such as this to the episodes grounded the show in a way that allowed viewers to connect with the teenage attitudes of the characters, and served as a stark contrast to the events around them. The juxtaposition of the Troubles violence and teenage life resonated with many viewers and critics alike, making it one of the features of the show that made it so successful.[33]

Cast members Saoirse-Monica Jackson, Jamie-Lee O’Donnell, Louisa Harland, Nicola Coughlan and Dylan Llewellyn appeared in a 2018 special episode of British game show, The Crystal Maze.[43] The episode raised money for Stand Up to Cancer UK and was well received by viewers and fans of the show.[44]

For the 2020 New Year holiday, the cast competed on a special episode of The Great British Bake Off. Cast members Nicola Coughlan, Jamie-Lee O'Donnell, Dylan Llewellyn, Siobhan McSweeney, and Saoirse-Monica Jackson all appeared for the special.

In GBBO fashion, there were three challenges to be completed and tasted by judges Paul Hollywood and Prue Leith. The first challenge was a trifle, then blinis in the technical round, finishing with a showstopper tiered cake that each member had to design in a decades theme. At the end of the competition, Saoirse-Monica Jackson was declared the winner.[45]

Fans of the show greatly enjoyed watching the actors interact with the judges and hosts, as well as with each other outside of character. Many positive responses were recorded on Twitter, praising the fun attitude, cast hijinks, and even calling for more crossovers with Derry Girls and GBBO.[46]