MILEY CYRUS caught fiance Liam Hems­worth texting “Mad Men” siren January Jones, and now she’s telling pals they’re kaput, say sources.

“Miley couldn’t believe it!” an in­sider told The ENQUIRER.

“As if the embarrassment over Liam’s fling with January wasn’t bad enough, to find out that he’s still in touch with her is pretty much the nail in the coffin as far as their rela­tionship is concerned.”

MILEY, 20, AND THE “HUNGER Games” hunk fell in love while film­ing the 2010 drama “The Last Song.” But they hit a rough patch after Liam, 23, was spotted leaving an Os­car party with Jones, 35, in February.

The two were reportedly seen “making out”at a private house party, and Miley was so enraged that Liam fled to his native Australia for three weeks in hopes that she would cool off.

Despite a brief reunion upon his return, things have gone from bad to worse for the couple.

“Hannah Montana” star Miley has been flirting up a storm with her ex Nick Jonas and model Patrick Schwarzenegger.

“She was also spotted smoking a suspicious-looking cigarette on her hotel balcony in Miami, where she partied hard at hip-hop mogul Pharrell Williams’ birthday bash.

Meanwhile, Liam cozied up to a mystery blonde in a Los Angeles bar on the same weekend.

As The ENQUIRER has reported, one person who’ll be thrilled that the romance has ended is Miley’s dad, Billy Ray Cyrus.

“BILLY RAY’S CONVINCED THAT Liam used Miley for fame, and all he’s done is embarrass her with his disrespectful behavior,” said a close friend of the “Achy Breaky Heart” crooner.

Added the source: “Miley has been telling pals that Liam is no longer interested in even try­ing to talk things through, and now she knows why. At least she found out about his roving eye before they tied the knot.”