Jack Osbourne Savagely Attacked at L.A. Coffee Shop

Jack Osbourne is the victim in a coffee shop attack -- his morning cup of Joe was brutally interrupted when a random stranger delivered a blow to his head in a totally unprompted attack.

Law enforcement sources tell TMZ ... Jack was at a coffee shop Wednesday in Studio City where he was sitting on the sidewalk patio. We're told someone who appeared to be homeless came out of nowhere and sucker punched Jack on the right side of his head. Jack, who had his back to the street, got up and threw his coffee at the guy ... who then ran away.

Our sources say cops were called and they found the attacker, who struggled with cops and needed to be tazed to calm the hell down. The suspect was ultimately arrested for battery and assault.

A rep for Jack tells us he is doing just fine.

The attack comes on the heels of Jack and his now ex-wife, Lisa, finalizing their divorce ... rather amicably too.

About a month ago, they reached a settlement that saw Jack pay Lisa a $1 million lump sum ... while he got to keep a bunch of their artwork.