W. David "Dai" John (birth unknown – death unknown) was a Welsh rugby union and professional rugby league footballer who played in the 1900s and 1910s. He played club level rugby union (RU) for Penygraig RFC, as a half-back, and representative level rugby league (RL) for Wales, and at club level for Salford, as a fullback or stand-off, i.e. number 1 or, 6.