Police are looking for a man who allegedly punched a referee from behind after an A-grade rugby league match at Calliope, near Gladstone.

A disgruntled rugby league fan has taken matters into his own hands, king-hitting a young referee from behind after a central Queensland A-grade game.

The referee, 20, had just finished refereeing an A-grade game at Calliope, near Gladstone, on Saturday night when an unknown man punched him in the back of the head.

Police say all they have to go on is the offender was wearing a black jumper and grey shorts.

The victim received minor injuries.