David "Dai" Rees Prosser (13 October 1912 – 6 May 1973) was a Welsh dual-code international rugby union, and professional rugby league footballer who played in the 1930s and 1940s, and coached rugby league in the 1960s. He played representative level rugby union (RU) for Wales and Glamorgan County RFC, and at club level for Glynneath RFC, Neath RFC and Swansea RFC as a prop, i.e. number 1 or 3, and representative level rugby league (RL) for Great Britain and Wales, and at club level for York and Leeds as a prop, i.e. number 8 or 10, during the era of contested scrums, and coached club level rugby league for Leeds.