EXCLUSIVE

Justin Theroux is in a nasty war with a neighbor who’s threatened to cut the actor’s water and electricity … according to a new lawsuit.

Justin and Jennifer Aniston are making renovations to their Greenwich Village co-op, and he says that’s not sitting well with the guy who lives downstairs from them. In the suit, Justin says the neighbor’s been bitching that the sound-proofing materials going in Theroux’s pad aren’t good enough. He’s demanding Justin spend an extra $25-30k to upgrade.

Justin says when he refused to give in, the neighbor launched a nasty campaign … including threats to cut the water and electricity lines that run to Justin’s roof deck, harassing construction workers at the home and perhaps worst of all … threatening to prune Justin’s ivy.

Them’s fighting words in the Village!

Theroux says the guy even threatened to set off a PR nightmare when he emailed … any legal action would be “opening the door to a broad range of allegations that would become publicly available, and which would not please Justin or his wife or their respective publicists.”

Justin is suing for at least $350k plus punitive damages.