Leon Small is a fictional character from the BBC soap opera EastEnders and its Internet spin-off EastEnders: E20, played by Sam Attwater. He made his first appearance in EastEnders on 5 January and appears in all twelve episodes of the first series of EastEnders: E20. The character was created by a team of 13 writers aged between 17 and 22 and is described as sexy and cool with a short fuse and a lack of respect for those in authority. The character's departure was announced on 11 May 2010 and his last appearance was on 30 September 2010.

Leon is one of four characters created for the first series of EastEnders: E20 who also appear in EastEnders. Along with the other characters from E20, he was created by the show's 13 writers during a summer school run by the BBC in August 2009. Open auditions for the cast were held at Theatre Royal Stratford East, and Attwater's casting was announced on 25 November 2009, on which he said "It is a great privilege to be working with such great actors and on such an established show. It's an amazing opportunity and I'm really enjoying tackling a character like Leon who has so much going on!" The first scene Attwater filmed was of him in his underwear, the first of six semi-naked scenes that were filmed for EastEnders: E20. Attwater said he felt pressure to be in shape for the part and prepared by attending a gym, saying "I want to be on the best form." Leon is also a dedicated boxer, but Attwater had never boxed before. His boxing scenes in EastEnders: E20 were filmed with a stuntman who Attwater was allowed to hit as much as was necessary.

Leon is described as sexy, effortlessly cool, with a short fuse and a lack of respect for those in authority. His mother died when he was a child and he was left in charge of his alcoholic father. In an interview with entertainment website Digital Spy, Attwater said the character is strong-minded, going on to say: "He's a boxer, he wins in the ring and he has a way with the ladies. He can talk most into bed! That's his strong attribute! Leon's mum died when he was young, and that was a big thing for him. His relationship with his father's quite rocky, so I think that's where his weakness lies, in his family life. He tries to push that away as much as possible." He said that during EastEnders: E20, "[y]ou see his strengths and weaknesses and by the end of it, he becomes quite a rounded character, which is taken on into the main series."

Along with his co-stars Emer Kenny and Ricky Norwood, Attwater's initial contract was extended to six months, and he hoped for it to be extended further, however, on 11 May 2010, his departure from the show was announced, along with that of Kenny, who played Leon's girlfriend Zsa Zsa Carter. The new executive producer of EastEnders, Bryan Kirkwood, said "Emer and Sam have made a real impact in the short time they've been on the Square and we wish them all the best for the future."

Leon arrives in the show's setting of Albert Square as a new student at Walford High School, and Peter Beale (Thomas Law) is to be his "buddy". Peter's twin sister Lucy (Melissa Suffield) takes a liking to Leon and holds a party in 89b George Street so she can spend time with him. The party turns to chaos and Lucy and Leon get everyone out by saying the police are outside. Leon offers to help Lucy clean up and asks her to join in a game of Twister with him. As they are playing, a condom falls out Lucy's pocket. Leon sees it and says he did not want to take advantage of her. However, she kisses him passionately, which leads to sex. After they have sex, Leon receives a text message and gets dressed but asks if Lucy wants to do it again. Lucy says yes, but after appears disturbed.

In EastEnders: E20, Leon and Lucy go back to the flat but are disturbed by Zsa Zsa Carter's (Emer Kenny) stepfather Andy who thinks she is inside. Lucy tells Andy where Zsa Zsa is, but Leon defends Zsa Zsa and Lucy leaves. He finds Andy attacking Zsa Zsa and fights him off. He then meets Fatboy (Ricky Norwood) and Mercy Olubunmi (Bunmi Mojekwu) and along with Zsa Zsa, they run from Andy into 89b George Street where they decide to stay. Leon tells Fatboy his mother is dead and his father has kicked him out. Leon and Zsa Zsa grow close, leading to them having sex in a cemetery. He begins to get frustrated with Zsa Zsa and grows closer to Mercy, and Fatboy accuses Leon of being the father of Mercy's unborn baby, though it is not true. Mercy suffers a miscarriage and Zsa Zsa freaks out and decides to leave. Leon stops her, saying he has feelings for her. He invites her to his boxing match, saying if she is there, he will know how she really feels. Leon wins the match but Zsa Zsa is not there. When they finally meet up they kiss, and knowing they can no longer stay in the flat, Fatboy offers them a room at his house.

Having started a proper relationship with Zsa Zsa, Leon returns to Walford looking for her after she runs away. He performs as a stripper at Bianca Jackson's (Patsy Palmer) hen party. After the party, Zainab Masood (Nina Wadia) catches him in bed with Lucy. Lucy tries to break Leon and Zsa Zsa up when they are kissing in The Queen Victoria public house, managing to drag Leon back to her house until her father Ian Beale (Adam Woodyatt) interrupts them and asks Leon to leave. Lucy watches Leon and Zsa Zsa around Albert Square and reveals to her stepmother Jane (Laurie Brett) that she is pregnant. Leon humiliates Whitney Dean (Shona McGarty) by filming her cleaning a bench in the Square and sending it to people, so when she hears Ian talking about the pregnancy, she decides to tell Leon. He confronts Lucy in The Queen Vic and asks if the baby is his. They meet the next day and he says he is willing to go with her to get an abortion, but she lies that the baby is not his. When Leon demands the truth, Lucy tells him she had an abortion.

Zsa Zsa receives gifts from someone calling themselves "The Blue Masquerader" and Leon grows jealous. Leon and Fatboy eventually discover that Peter has been sending the gifts. Lucy helps Peter to split up Leon and Zsa Zsa but after Peter changes his mind, Lucy reveals to Zsa Zsa that Leon got her pregnant. Zsa Zsa breaks up with Leon and his attempts to win her back fail. Leon moves back in with his father but moves out again when he beats Leon after finding out he got Lucy pregnant. Leon tells Fatboy he is staying with someone but later sneaks back into 89b George Street. He helps Whitney with her T-shirt printing and flirts with her and kisses her, but she does not reciprocate as she has a boyfriend, Billie Jackson (Devon Anderson). He later tells Peter and Fatboy about it, and subsequently Lucy finds out and tells Billie, which leads to him ending his relationship with Whitney, who knees Leon in the groin while Fatboy attempts to get Leon and Zsa Zsa back together, as Leon has not been himself since they split up.