The couple, who were recently said to be "re-evaluating" their relationship, called it quits last week, reports US Weekly.
"They are broken up," a source told the publication. "It's sad, she cares about him a lot and thinks he's a great guy but they really hit a rough patch.
"[Cy's] found it difficult to live his life with her in the spotlight and that's what caused their split. No drama, it's amicable, but things didn't work out."
Hilton and Waits began dating in August 2010, shortly after Hilton's split from ex-boyfriend Doug Reinhardt.
Hilton recently insisted that she was "so happy" with Waits as the pair approached their one-year anniversary.
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