Lydia Hart is a fictional character from the British Channel 4 soap opera Hollyoaks, played by Lydia Kelly. Lydia was created by series producer Bryan Kirkwood as one of many characters introduced that year. She made her debut in the soap on 4 March 2009, and remained for ten months.

Lydia's storylines focus on homosexuality, obsessiveness and murder. The seemingly level-headed music lover and friend of Josh Ashworth (Sonny Flood), she is portrayed as opinionated, passionate young student who had a love of music and protecting her family, including her young sister Persephone Hart (Elizabeth Hadley) who also appeared in the show for a period of three months. Lydia's relationship to the sexually confused Sarah Barnes (Loui Batley) was central to the character for the seven months leading up to her screen death in October 2009 after she was murdered by Lydia. Other storylines included her ongoing on-off relationship with ex-girlfriend Charlotte Lau (Amy Yamazaki) and continued feuds with Archie (Stephen Beard) and Zoe Carpenter (Zoë Lister). The character's departure was announced in December 2009, resulting in the character being charged for the murder of Sarah and the attempted murder of Zoe, with Lydia making her final appearance on 1 January 2010. The parachute stunt won a British Soap Award in 2010, but the aftermath storyline has received mixed reviews from critics. Some have favoured Lydia's "bunny boiling" whilst others described it as a "drawn out and boring storyline."

In November 2008, during an episode of Hollyoaks spin-off Hollyoaks Later, Sarah Barnes (Loui Batley) and Zoe Carpenter (Zoë Lister) had a sexual encounter. Up to now both characters had previously been portrayed as heterosexual and this was the start of Sarah's on-going sexuality crisis. The character of Lydia Hart was created as the new love interest for the sexually confused already established character, Sarah. When the character first appeared on-screen she was revealed to have a younger sister, Persephone Hart (Elizabeth Hadley), who was attending the dance classes taught by Sarah. Little is known about the rest of Lydia's family, although the character did stay with her mother frequently off-screen. The character was also given links to Charlotte Lau (Amy Yamazaki) who arrived in Hollyoaks in June 2009. It was soon revealed that Lydia was Charlotte's ex-girlfriend.

It was announced in February 2009 that Hollyoaks series producer Bryan Kirkwood had cast television newcomer Lydia Kelly in the role of Lydia. Speaking to the Hollyoaks website of her casting, Kelly stated, "It was brilliant, when my agent said I'd got the part I didn't believe her." In Hollyoaks Backstage, when Kelly was asked what was next for Lydia, she stated, "[...] I don't know whats next for Lydia [...] I think justice has to be done soon." In December 2009, it was announced that Kelly would leave the show. Producers confirmed that Lydia would depart at the climax of her storyline.

Lydia first arriving on-screen was first shown as different from other characters and it was stated from her inception that she was passionate about music and enjoyed getting people into the music scene. Speaking of her character, Kelly stated "She's very down to earth. She knows exactly what she wants, where she wants to go, and how to get there! She's also very level-headed." From the characters inception, she was shown to be an opinionated, proud young student who wasn't afraid of her homosexuality and a person who could make friends very easily, as well as enemies.

Lydia's relationships helped develop the character. Her first relationship off-screen is with ex-girlfriend Charlotte, who supposedly shared her interests in music and fashion, as they were both considered 'out there'. The history of the relationship immediately gave viewers an insight to the character. However, their relationship was seemingly shattered by Lydia's constant jealousy and her clingy nature, which ultimately led to their break up. Lydia tried to commit suicide soon after, which was told on-screen when Charlotte arrived in the village. Lydia's second relationship was a more serious one, with the sexually confused Sarah Barnes. Sarah, who had previously been portrayed as heterosexual, suffers an identity crisis, coming to terms with her one-night stand with Zoe Carpenter; however Sarah ended the relationship after Lydia became interfering and tried to control her life due to falling in love with her. Speaking to entertainment website Digital Spy about Sarah's relationship with Lydia, Loui Batley commented, "With Lydia, she brought something to her and she got on with her and was sparky, which is something that Sarah liked." After her relationship with Sarah ended, the character's true persona was revealed. She became jealous of Sarah and her relationship with Zoe, and the character's vulnerability became the centre of her deranged campaign for revenge in the latter part of 2009, as she was excluded from Sarah's life.

In July 2009, it was announced by Hollyoaks that Loui Batley had quit her role as Sarah and Zoe Lister (Zoe) would depart the soap later in the year and that one of the girls' exits would result in a "tragic curtain call". It was announced that Lydia would be the cause of the pair's departure. In later September, Lydia became very jealous of Sarah, who she had recently split up with. She also became jealous of Zoe, who Sarah had a one-night stand with in the previous year. During the events of Hollyoaks Later in October, Lydia's jealousy went out of control when she sabotaged a parachute, which was revealed to be used by either Sarah or Zoe. It was announced that one of the pair would be killed after plummeting to their death.

Hysterical Lydia, who thought Sarah and Zoe were having an affair, had a conversation with Charlotte where she revealed attempting suicide after splitting up with her, proving the character's vulnerability. After sabotaging Zoe's parachute, they are mixed up and a terrified Lydia began to worry that she might have got the sabotaged parachute. While doing the jump, Zoe's deploys, however Sarah's does not. As Sarah hits the ground, Lydia screams in terror. She is completely destroyed by Sarah's death, but does not admit to being responsible when Zoe is arrested, after which Lydia tries to commit suicide once again.