Rhys Haydn Williams (14 July 1930 – 27 January 1993), born in Cwmllynfell, was a Welsh rugby union lock forward who gained 23 caps for Wales and ten consecutive caps for the British Lions.

In his later life he became a sports administrator, including the role of vice-president of the Welsh Rugby Union.

Rugby historian John Griffiths described Williams as "the finest line-jumper in the world" and "the most accomplished British lock of the 1950s".

Between 1954 and 1959 Williams played 22 matches for the Barbarians, a record number of games for a Welsh player.

Andrew Bennett in his book Welsh Rugby Heroes includes R. H. Williams at No.