NFL Lineman -- Fights Off Home Intruder ... Gets Restraining Order

A frightening moment for Oakland Raiders lineman Donald Penn -- who fought off a home intruder who kicked in his front door and threatened his family earlier this month ... TMZ Sports has learned.

According to court docs obtained by TMZ Sports, Penn -- who's 6'4", 340 lbs. and a former Pro Bowler -- was at his L.A. home with his wife and kids when a large man hopped over his security gate, busted in his front door and began going crazy inside the home.

That's when Penn -- who was with his wife and 2 young children at the time -- sprung into action ... physically restraining the man (who's 6'1", 220 lbs.) ... until cops showed up.

Sources tell us ... Penn is adamant he has no connection to the man -- and doesn't know why he was targeted.

Penn eventually filed for a restraining order against the guy, which was granted -- and now the suspect has been ordered to stay at least 100 yards away from Penn and his family.