Hirwaun born, Rhys Williams represented both his local club and Abercynon RFC at junior and youth level, whilst a pupil at Aberdare Comprehensive School.
Gaining international honours with Wales at under 16 and under 18 level, Rhys was also involved with the Blues regional Academy. Whilst still only seventeen years of age Rhys was invited to join the Pontypridd senior squad in the summer of 2007, belying his youthfulness with some abrasive performances in the club's premiership campaign.
He captained Wales U18 in their first capped international match of the 2007–2008 season against England U18 in March 2008.
He made his Blues debut in September 2008 coming off the bench against Connacht when the Blues ran in a record 58-0 score at the Arms Park.
Steady progress was made by the industrious hooker, his efforts were rewarded with a call-up for the Wales under 20s, as captain of the squad in 2009 and selected for the Wales under 20’s squad for the Junior World Championships in Japan in June 2009.
Williams made his Heineken Cup debut as part of Phil Davies’ young side in 2012 when the Blues welcomed Montpellier to the Arms Park.