David "Dai" Greene (born 11 April 1986) is a Welsh hurdler who specialises in the 400 metres hurdles, competing internationally for both Wales and Great Britain.
In a 'golden' sixteen-month period between 2010 and 2011, Greene won the World, European, Diamond League and Commonwealth titles in the event, in addition to winning the event as part of both the European Team Championships and the IAAF Continental Cup.
He is the second fastest British man over the 400 m hurdles, behind the British record holder, Kriss Akabusi.