Justin Bieber -- I'm Done with Los Angeles

Justin Bieber has cut his final ties with the city of Los Angeles ... because TMZ has learned he's sold the last piece of property he owns in the area ... leaving him wide open for a permanent move to the ATL.

As TMZ first reported, Bieber sold his Calabasas home to Khloe Kardashian for a cool $7.2 million ... making a little over a million on the sale.

But according to our sources, Bieber also owned the 1.7-acre plot of land next door ... until now. We're told Bieber just sold that for $2.775 million (he bought it for $2.35 mil in 2012) and the deal closes in 30 days.

As for the buyer, our sources say it's nobody famous, but he's about to inherit a slew of famous neighbors.

We're told Bieber had been looking for another home in the Los Angeles, but he's since called off the search.