The Pirates Of The Caribbean star forked over the hefty sum for a 19-room ranch in Tennessee, as Amber, who he met on the set of The Rum Diary last year, is a keen horse-rider.
A source told The Sun: "Buying this house is the surest sign yet of how serious Johnny is about Amber. She's always dreamt of having a ranch. They were going to buy one in Texas, where she's from, but they fell in love with the Nashville property as soon as they set eyes on it."
The insider continued: "Johnny isn't bothered about living it up in Hollywood, he'd rather have the good life. While Amber loves to ride horses, Johnny's serious about writing and playing music."
Johnny, 49, split from long-time partner Vanessa Paradis, the mother of his two children, in June.