X Ambassadors
Songs: Unsteady - Sucker for Pain - Renegades - Happy People (& Teddy Swims & Jac Ross) - Boom

X Factor
Joe McElderry, Leon Jackson, Same Difference, The X Factor Finalists, Alexandra Burke, Steve Brookstein, Shayne Ward, Leona Lewis, Susan Boyle, Jedward, Maria Lawson & Cher Lloyd
Songs: Hallelujah (Alexandra Burke) - A Moment Like This (Leona Lewis) - Hurt (Leona Lewis) - Hero (Help for Heroes (H4H)) - Sorry Seems to Be the Hardest Word (Leona Lewis)

Xanadu (film)
Music from the Motion Picture (1980)
See also: Xanadu (musical), Olivia Newton-John, Cliff Richard & Electric Light Orchestra
Songs: Xanadu (Olivia Newton-John & Electric Light Orchestra) - Suddenly (Olivia Newton-John & Cliff Richard) - Whenever You're Away from Me - Dancin' (& Olivia Newton-John & The Tubes) - Don't Walk Away (Electric Light Orchestra)

Charli XCX
Charlotte Aitchison
Songs: I Love It (& Icona Pop) - Guess (feat. Billie Eilish) - party 4 u - The Girl, So Confusing (version with Lorde) - Spring Breakers

Xscape
Songs: My Little Secret - Understanding - Tonight - Just Kickin' It - The Arms of the One Who Loves You

XXXTentacion
Songs: Hope - Again (& Noah Cyrus) - Falling Down (& Lil Peep) - Sad! - Fuck Love (& Trippie Redd)