Alison King was born on March 3, 1973 in Leicester, Leicestershire, England. at Leicester Royal Infirmary to Alex and June King, who were both nurses at the hospital. She was their fifth child and third daughter. She went to Markfield Mercenfeld Primary School and South Charnwood High School, where she first took an interest in acting. She continued to act while attending Groby Community College, where a teacher would offer drama and dance classes to students in their free time. Alison was raised as a Christadelphian and attended the Christadelphian Church at Westleigh, Leicester, where she was baptised as a teenager. At the age of 18, she moved to Newquay, Cornwall, and worked at Fat Willys Surf Shack. While on holiday in the Mediterranean, in a Tenerife bar in March 1995, she met Philip Middlemiss, who became her boyfriend for five years and encouraged her to become an actress. At the age of 22, she enrolled at the North Cheshire Theatre School. In the 1990s, King was described as a regular on the Manchester party scene while dating Middlemiss, and commented in 2007 about her party animal days, saying "it seems like another life time ago. That gap from 25 to 34 is a long time. Sometimes I meet somebody from 10 years ago and I can't remember anything." During her time at drama school, she got her first television role, playing Helen, a hair salon crimper, in two episodes of Brookside (1982). Before the conclusion of her three-year diploma, she was cast in the major role of Lynda Block in Sky One's İkili takım (1997) for three years before the character was sent to prison. She reprised the role some years later.

During her break from working on Dream Team, she worked on several projects abroad including appearing as an extra in the American feature film Şangay Şövalyeleri (2003) as a prostitute in a scene alongside Jackie Chan and Owen Wilson. She gained supporting roles in BBC comedy-drama Help (2005), a Steven Seagal direct-to-video film Submerged (2005) and the little-seen feature film Final Contract: Death on Delivery (2006). She talked of her enthusiasm for filming action scenes "I always think you should do the slap for real. They always have a safety guy on set anyway. I've done a lot of action films actually - I like getting involved. I've kicked people, shot them and all kinds of things."

She played Frenchie in a production of Grease (1978) in Edinburgh Festival Theatre, and narrated a production of Blood Brothers in the London Palladium. In 2000, she appeared in an episode of Cold Feet (1997) as "Girlpower", a seductive Internet avatar. In the early 2000s, she made one-episode appearances in several television shows, including the final episode of Mile High (2003), playing the wife of Captain Nigel Croker's, and Coupling (2000) in the episode "The Man with Two Legs", as Chrissy with whom Jeff Murdock becomes infatuated on his morning train ride. She also appeared in the second episode of the fourth series of Auf Wiedersehen, Pet (1983) in 2004. She played one of the prominent roles for two independent films, Save Angel Hope (2007) and Back in Business (2007).

In 2006, she was cast as Carla Connor in the ITV soap opera Coronation Street (1960), which proved to be her breakout role. She made her first appearance in the role in the episode broadcast on 1 December 2006. She had previously appeared in the soap in 2004 as an unrelated character named Mrs Fanshaw. Her one-episode role was part of a larger storyline to "sex up" Ryan Thomas's character, builder Jason Grimshaw. She later joked "I was Mrs Fanshaw - or Fanny. What a nightmare!" She said that she initially found the role difficult, as she "was uncomfortable playing a constant bitch at first. I'm getting into it now but I'm not as nasty or as cocky as Carla. She's horrible to anyone she perceives to be a rival. I couldn't be like that." In November 2010, she admitted her character "annoys the hell" out of her, and she has also said she hates the voice she chose for the character.

After becoming pregnant in 2008, Alison went on maternity leave in 2009. In a November 2008 interview, when asked about filming scenes while pregnant, she joked "Yeah, I'm big and fat at the minute. I'm just getting fatter. It's a competition between my boobs, my bump and my ass! I think my bum's slightly ahead at the minute! I look like Humpty Dumpty with leggings."

Alison's role in the soap involved high-profile storylines. In 2010 she was involved in the death of Tony Gordon storyline, in which she had to be kidnapped in the Underworld factory. For these scenes, she had to be tied to a chair with her hands tied behind her back and have her mouth gagged with gaffer tape. Of filming the scenes, she said "We were tied up and gagged for a week and a half. I was gaffa-taped for a little while and tied up for most of it. My wrist was sore at the end! It was a different experience anyway, acting for two weeks with your hands tied behind your back on a chair." Alison said the Siege Week was "great television and I'm really pleased to be part of it", and performed all stunts herself, except one that consisted of a jump from a balcony. The storyline was a hit with audiences and critically acclaimed.

Alison participated in a live episode to commemorate the show's 50th anniversary in late 2010. In September 2011, her character Carla was raped by her fiancée Frank Foster, whom she was unaware was a sexual predator. The storyline was announced in June, and producers insisted they had consulted domestic abuse charities. This storyline had a massive public impact and saw a high rise in reported rapes across the United Kingdom. Alison spoke of how there was an 800% increase in calls to support organisations after the storyline had aired, and that people had contacted her about their real-life experiences, some of whom she has kept in communication with. She said that she was "proud" of the storyline. Her performance in the rape storyline led to a Best Actress award at the 2012 British Soap Awards. When her nomination was announced, King called it "lovely, it was really nice to hear. I'm delighted." She said that she got "choked up" when she won. She admitted the rape storyline left her "physically and mentally exhausted", but in a January 2016 Q&A called it her favourite storyline of her own from the show. In January 2015, she was involved in a high-profile storyline involving a mini-bus where she almost dies, escaping from the mini-bus before it falls from a cliff.

In May 2015, it was announced she would be taking an extended break from Coronation Street to pursue other projects. She also initially stated her intention was to take a break from the show and return. However, in January 2016, it was confirmed that the departure would be permanent. She said of her reason to leave: "I've probably only ever done about 20 pick-ups or drop-offs in all the time my daughter's been at school, which is quite sad. And creatively, I miss being other people. It's what I went to drama school for. I love playing diverse characters and meeting new people. And, truthfully, I also want to be able to get my voiceover career going again. There's all sorts of things that I used to do, which I can't do while I'm on Coronation Street. So, those are the reasons, really." She departed on 26 May 2016 and in an interview said that she would be looking for new types of roles and projects, and saying said she would continue to watch Coronation Street. Before leaving, she was nominated for Best Serial Drama Performance at the 2016 National Television Awards, but lost to Danny Dyer. In August 2017, after numerous rumours earlier in the year, it was officially announced that Alison would return to her role as Carla Connor in December that year after being lured back by the show's new producer Kate Oates. She returned to filming Coronation Street on 10 October 2017. While on her break from Coronation Street, she filmed four episodes as Superintendent Henchy in the second series of Sky Atlantic comedy Sick Note (2017).

Alison is considered by the British press and public as a sex symbol. Her physical appearance and personality is considered popular within the United Kingdom male demographic. In December 2008, she was voted the top 'Sexiest Soap Babe Of 2008' in an online poll of the British public by MSN Entertainment, followed by Lacey Turner and Roxanne McKee in second and third place. She has been voted sexiest female for her role as Carla Connor on Coronation Street (1960), was nominated for Sexiest Soap Star at the TV Now Awards in 2008, and Sexiest Female at the 2011 British Soap Awards but lost to her Coronation Street co-star Michelle Keegan. She has been named as one of the "sexiest soap females". In August 2012, Maxim named her number one of the Top Ten Sexiest UK Soap Stars. Scottish Daily Record has called her "dreamy", while Daily Mirror has referred to her as "effortlessly gorgeous", and its readers voted her as one of the Sexiest Female soap stars. Columnist Grace Dent described her as "an alluring vision, raven haired, classy, sultry and replete with guile".

Alison has said she is "flattered" to be considered a sex symbol, speaking in 2010 of her surprise "I don't know that I am - but yeah, why not? I've just turned 37, so way to go! They can call me a sex symbol if they want." She spoke in 2007 that she hoped to remain popular with male viewers, saying "I'm thankful that people think I'm sexy, especially as I'm getting on a bit. But if they saw me first thing in the morning they may change their minds!" When asked about her nomination for Sexiest Female at British Soap Awards, she laughed "If I win it, I'll eat my own hat. I don't think Carla is sexy, I think she's just a bit gobby. I don't really see her as a sexpot."

In April 2004, Alison was chosen as the face of Boddingtons beer, taking over from Melanie Sykes. She launched the ad campaign at The Circle Club in Manchester. She said she was "thrilled to be chosen as the girl to deliver that infamous endline in a Boddingtons ad. As a girl who spends so much time in Manchester, it's great to be able to be part of a campaign for a brand such as Boddingtons, especially as I love a creamy pint of Bodds down my local." She made appearances in a series of recurring television adverts for Daz.

During her five-year relationship with Philip Middlemiss, Alison was the subject of press attention due to his fame on Coronation Street, which she would join a decade later, such as when in August 1996, Middlemiss and Alison, then 23-years old, were spotted staying at the Dromoland Castle in Newmarket-on-Fergus, prompting speculation that they they would get engaged. In November 1996, Middlemiss told Scottish Daily Record of his relationship with King "I've never been happier. She is a wonderful girl. I love her to death." Middlemiss has said the couple did not break up but drifted apart. In a July 2000 interview, he said of their relationship "I was in love with Allie. She's the only person I've ever really loved. But she was working in London and I was in Manchester. In another life, if I had been a bus driver and she had worked at the local baker's shop, we would have got married and had kids by now." In 2006, she became engaged to fellow actor Jim Alexander who co-starred in several series of Dream Team with her, as well as the Daz adverts. The couple shared a flat in London. However, the pair split in early 2007. The breakup was reported to be because of King's new role on Coronation Street as Carla Connor, as their relationship became strained when she moved to Manchester in order to star in the soap opera. In January that year, she had said "He's making me very happy and bounding up between London and Manchester. He's coming up for a month in a few days, so I'm looking forward to that very much." A friend of King's said she was "devastated" by the breakup and that she had thrown herself into her work to cope with the loss.

She dated Adam Huckett, a Coronation Street sound technician from April 2007, just two weeks after breaking off her engagement to Jim Alexander. She gave birth to their daughter, Daisy Mae, on 11 February 2009, in a Manchester hospital. She delivered the baby by Caesarean section. King has also stated that she wishes to have more children in the future, and loves being a mother. King admitted she initially struggled with motherhood and "cried down the phone to Julia Haworth for hours. She was sweet." In a 2010 interview with Scottish Daily Record, she said "I love motherhood. My daughter is hilarious. She just makes me laugh every day." When asked in October 2009 if she and Huckett would marry, she said "Probably. Eventually. If he gets a ring!" She became engaged to Huckett in September 2011 while on a trip to Paris. However, on 16 October 2012 it was reported that the engagement was off as they had split up. King had taken a four-month break from Coronation Street between June and October to go on holiday with Huckett and their daughter. They claimed they had split as they "weren't making each other happy anymore". They said they were "determined" to remain friends, denied anyone else was involved, and confirmed they would still work together on Coronation Street. Since 2016, she has been dating Hollyoaks (1995) assistant director Paul Slavin. The relationship was revealed after they were photographed by the press and there was speculation as to his identity. She said of the relationship: "I'm seeing somebody. It's very early days so I don't want to say anything more, but I'm happy."

Alison fronted a campaign to raise money for Breast Cancer Campaign with thermal manufacturer Damart in 2007, and in November 2015, wrote a column for The Mail on Sunday describing a holiday to Villa Irida, Corfu with her daughter and best friend.