X Ambassadors
Songs: Happy People (& Teddy Swims & Jac Ross) - Sucker for Pain - Unsteady - Blinding Lights - 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) - Wild Horses (Susan Boyle) - A Moment Like This (Leona Lewis) - Against All Odds (Steve Brookstein) - When You Believe (Leon Jackson)

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) - Don't Walk Away (Electric Light Orchestra) - Magic (Olivia Newton-John) - Suddenly (Olivia Newton-John & Cliff Richard) - Whenever You're Away from Me

Xavi
Also known as Joshua Xavier Gutierrez Alonso
Songs: La diabla

Charli XCX
Charlotte Aitchison
Songs: Von Dutch - I Love It (& Icona Pop) - Vroom Vroom - Fancy (& Iggy Azalea) - Boom Clap (The Fault In Our Stars)

Xscape
Songs: My Little Secret - Just Kickin' It - Understanding - Keep On, Keepin' On (& MC Lyte) - Do You Want to

XXXTentacion
Songs: Hope - Changes - Moonlight - Sad! - Falling Down (& Lil Peep)