Johnny Depp is looking to buy a medieval castle in the Italian countryside ... but the town isn't sold on having him, even though we know he'd show deference as a neighbor.

Sources with direct knowledge tell TMZ ... the actor recently toured a castle in Montalto Dora, Italy -- a small town with a little over 3,000 people living there -- as a potential addition to his real estate portfolio. However, we're told nothing is official ... but he is considering a buy.

The castle is valued at about $4 million, and it's for sale ... if he is interested in claiming it as his own.

Reports have suggested the townspeople aren't thrilled over the notion of having JD move in ... but despite this, we're told Johnny would prove them wrong if he were to snap it up.

Our sources say he'd respect any guidelines or regulations imposed on the property -- assuming this purchase came to fruition ... which, for now, isn't a sure thing. Actor Riccardo Scamarcio reportedly gave Johnny the tour ... this as they shoot a movie together.

The town's mayor, Renzo Galletto, told the Post Johnny might not be the best person to move in ... and would likely cause more harm than good, especially economically.

Since the castle has undergone quite a bit of restoration over the years, the mayor defends the estate as a site of community interest -- which means they're keeping a watchful eye over the property, but like we said ... if Johnny bought it, he wouldn't be a burden anyway.