Stacey Slater (also Branning and Fowler) is a fictional character from the BBC soap opera EastEnders, played by Lacey Turner. She first appears in episode 2826, originally broadcast on 1 November 2004. The character is introduced as a feisty and troublesome teenager and extension to the established Slater family. She was created by scriptwriter Tony Jordan with Turner in mind. Producers explored the character's backstory with the introduction of her mother, Jean Slater (Gillian Wright), who has bipolar disorder. They then paired Stacey with Bradley Branning (Charlie Clements) and writers developed a series of problems for their marriage, including an abortion and Stacey's scandalous affair with Bradley's father, Max Branning (Jake Wood). In 2009, the character was placed in an issue-led storyline when she was diagnosed with bipolar disorder; the show worked with various charities to develop the story. Writers also incorporated Stacey in the "Who Killed Archie?" plot and revealed her as his killer in a live episode, which was followed by a two-hander episode between Stacey and Max. Stacey became pregnant by Ryan Malloy (Neil McDermott) and gave birth to their daughter Lily Slater. This led to a feud between Stacey and Ryan's wife Janine Malloy (Charlie Brooks), and culminated in Stacey fleeing Walford on the episode broadcast on 25 December 2010, to avoid imprisonment after Janine stabbed herself and framed Stacey for attempted murder. Turner's return was announced on 19 December 2013, and Stacey reappears in the episode originally broadcast on 7 February 2014 before departing again on 24 March 2014. She made a permanent return on 1 September 2014. On 12 May 2025, Turner announced she would depart the role later in the year to focus on her family and new work opportunities; she revealed she was open to returning at a future date. Stacey departed on 2 October 2025, with Turner affirming she would eventually return to the role.

Following her return, Stacey embarked on an on-off relationship with Martin Fowler (James Bye). She became involved in another issue-led story exploring postpartum psychosis in 2016, following the birth of her son Arthur Fowler. She then married Martin and gave birth to their daughter Hope Fowler. Turner went on maternity leave in August 2019 and prior to her exit, Stacey became involved in a custody battle with Kush Kazemi (Davood Ghadami) and a feud with her cousin Kat Slater (Jessie Wallace). After attacking Phil Mitchell (Steve McFadden), Stacey flees the square and is off-screen for thirteen months, making a cameo appearance on 28 October 2019 in between before fully returning in September 2020. Turner took a second maternity leave in April 2021 and Stacey departed for six months, after being falsely imprisoned for GBH. While in prison, she divorced Martin and married her female in-mate Eve Unwin (Heather Peace) to secure her release from prison. She made two cameo appearances on 16 and 20 September 2021, before returning permanently on 25 October. Stacey's storylines since her return have focused on supporting Jean through another bipolar episode and discovering that her daughter Lily (Lillia Turner) is pregnant at the age of 12 amidst financial difficulties, causing Stacey to sell lingerie photos of herself for money on SecretCam, an OnlyFans-style website. Stacey is later stalked by her subscriber who is revealed to be Lily's tutor Theo Hawthorne (William Ellis). Theo attempts to rape Stacey but she is saved by her cousin Freddie Slater (Bobby Brazier); Stacey and Eve try to protect Freddie from going to prison by framing Theo for attempted GBH, but Theo is eventually sent down for his crimes. On Christmas Day 2023, Stacey helps to cover up the murder of Keanu Taylor (Danny Walters) during "The Six" storyline, and later has an affair with Jack Branning (Scott Maslen).

The character has proven popular, and Turner has won over thirty awards for her portrayal, the most for any actor or soap in the UK. Her accolades include four National Television Awards, six British Soap Awards and eight Inside Soap Awards.

In September 2004, an official BBC press release announced an addition to the popular Slater family; the new "feisty female" named Stacey Slater, Charlie Slater's teenage great-niece and cousin-once-removed to Lynne, Kat, Belinda and Little Mo, and second cousin to Zoe. According to the report, Stacey "looks like a Slater and shares the same family attitude but with one difference—Stacey is one hell of a bitch! [...] She is going to be trouble!"

16 year–old actress Lacey Turner was cast in the role. Turner had originally auditioned for a part in the Miller family, but was given the part of Stacey instead. Commenting on her role, Turner said "I was speechless when I found out that I had been cast as Stacey Slater especially as I knew I would be working with Jessie Wallace who is my favourite actress. I've watched the show since I was about four years old, and I used to live in a house that backed onto the EastEnders set so I used to watch them filming all the time. I always dreamt of being on the show and so I can't believe that I've fulfilled my greatest ambition!" She added, "I'm not like Stacey at all although I love playing her! She's a real challenge [...] I think people are going to love to hate her like they did with [the character] Janine Butcher."

EastEnders scriptwriter Tony Jordan revealed that he created the character with Turner in mind: "I first met Lacey when she came to a casting workshop for the Miller family ... She was leaning against a wall and looked just like Kat Slater, played by Wallace. I thought she would be perfect for the Slater family so I wrote in Stacey's character especially for Lacey."

The character appears to be tough, stubborn, fiery and very bitchy, however, as Turner explains, this is just a front and "underneath she's very vulnerable". Turner has described her character as a cross between two other EastEnders characters, Janine Butcher and Kat Slater, saying: "She's very naughty, but she has her reasons for her nastiness."

Over the course of the character's narrative, it was revealed that one of the reasons for Stacey's tough and malicious exterior was her troubled family life — specifically the death of her father, disappearance of her brother, and her mother's bipolar disorder. Addressed in a storyline that aired in December 2005, Stacey returned to live with her "disturbed" mother Jean, played by Gillian Wright, during one of her breakdowns. Jean, who "sank into the dark despair of her illness", was living in squalor, off her medication, starved, suicidal, and being abused and ridiculed by her neighbours. Stacey was forced to admit her to a mental institution for her own safety. The storyline won a Mental Health Media Award in September 2006.