Ariana Grande will have a court-ordered force field around her for the next 5 years -- which will hopefully deter an obsessed fan who was arrested on her property 2 months ago.

A judge just signed off on a permanent restraining order for AG's mother, Joan -- which also extends to Ariana -- which will run through May 5, 2025. Under the order, Fidel Henriquez -- the man in question -- can't come within 100 yards of Joan's home, her vehicles ... and of course, her and Ariana. Basically, he's gotta stay the hell away.

The guy's also been instructed not to harass, threaten, intimidate or contact them in any other fashion -- which covers everything from written correspondence to phone calls as well as any form of electronic messages, including texts and social media DMs.

We broke the story ... Henriquez was hit with a TRO after he got busted for trespassing on their property back in March. They said they were scared for their lives and needed a judge to step in.

You'll recall ... Henriquez is alleged to have slipped onto the property by following a delivery truck through the gates, and once inside ... cops say he was rummaging through the garbage before knocking on Joan's front door, with a love note to Ari in hand.