Elizabeth Gillies' husband filed a restraining order against their neighbor ... this after they claim he strolled into their home, following a rough and long history of next-door headbutts.
Per court docs, obtained by TMZ, the ex-"Victorious" star's hubby -- music producer Michael Corcoran -- is asking a judge to grant him and EG a TRO against their Toluca Lake, CA neighbor, who they say lives within earshot... claiming the man walked into their home on multiple occasions, including as recently as the beginning of this year.
The paperwork says Elizabeth, Michael, and a couple of friends spent New Year's Day at the house, which they usually rent out, when the neighbor strolled in 2 times -- and also allegedly tried unlocking the front door 2 days later.
Michael says he has a long-standing issue with the neighbor, calling him a "violent, disturbed, intrusive, and threatening individual" ... and believing he "harassed and spied" his last tenant so much, they had to move out.
He also believes he's been losing out on rental income, thanks to the neighbor ... because he has to warn potential renters about the nuisance next door before moving in.
He claims the neighbor's done wild things over the years -- like shouting out front at 1 AM about hiring an investigator to follow his tenants, pounding on the front door, and calling the cops multiple times ... and one instance led to police pulling up with guns drawn.
Michael claims the neighbor called police on his tenants on Thanksgiving 2022, claiming they were "killing babies" in the backyard ... which prompted cops to arrive, frisk one of the men inside, and search the whole property -- finding nothing.
The docs say cops have already told Michael and Elizabeth's neighbor to leave the tenants alone, but it appears to be falling on deaf ears ... which is why he's asking for a restraining order that protects both of them.
A judge has yet to rule on their temporary restraining order request.