A man's home is his castle ... unless it's a dude who lives in a shoe box of an apartment in New Jersey that's too small for his life-size replica of the "Game of Thrones" throne.
Mike Ross tells TMZ ... he won a reproduction of the Iron Throne in an HBO fan contest ... it was just delivered to his Hoboken apt. Problem is ... it's 7'2" tall and 350 lbs -- and it doesn't fit.
For now ... he's sticking it in an even less regal setting -- his parents' garage.
It's an awesome chair ... a $30K hand painted fiberglass knockoff made to look like it was constructed with swords ... just like the one crafted by Aegon I Targaryen, the first king of the Seven Kingdoms.
Mike says he loves it ... but is open to offers from other GoT fans.
He wants to use the money ... for a down payment on a bigger place.