X Ambassadors
Songs: Unsteady - Happy People (& Teddy Swims & Jac Ross) - Blinding Lights - Boom - Renegades

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) - The Climb (Joe McElderry) - Wild Horses (Susan Boyle) - When You Believe (Leon Jackson) - A Moment Like This (Leona Lewis)

Xanadu (film)
Music from the Motion Picture (1980)
See also: Xanadu (musical), Olivia Newton-John, Cliff Richard & Electric Light Orchestra
Songs: All Over the World (Electric Light Orchestra) - Don't Walk Away (Electric Light Orchestra) - I'm Alive (Electric Light Orchestra) - Xanadu (Olivia Newton-John & Electric Light Orchestra) - Suspended in Time

Charli XCX
Charlotte Aitchison
Songs: Speed Drive (Barbie (2023 film)) - I Love It (& Icona Pop) - Fancy (& Iggy Azalea) - Vroom Vroom - 1999 (& Troye Sivan)

The xx
Songs: Crystalised

XXXTentacion
Songs: Roll in Peace (& Kodak Black) - Changes - Moonlight - Falling Down (& Lil Peep) - Hope