Every once in a while, you hear a pop song so undeniably catchy that it makes you stop and wonder: "Where have I heard this before?"

Like any other industry, the music business is rife with lawsuits, particularly those surrounding copyright infringement—in which another artist, songwriter or producer claims that that big pop song on the radio was totally copped from one of their own songs.

It's happened to the best of 'em: Lady Gaga, Demi Lovato and Ed Sheeran are just a handful of stars who have been hit with music-related lawsuits.

Whether they've won their cases, settled out of court or had lawsuits dismissed altogether, these nine pop stars, below, were once embroiled in legal battles with other artists and music personnel.