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 Williams 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 Under-18 in their first capped international match of the 2007/08 season against England Under-18 in March 2008.
Williams 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 BT Sport Cardiff 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- 20s squad for the Junior World Championships in Japan in 2009.
Williams made his Heineken Cup debut in 2012 when the Blues welcomed Montpellier to the Arms Park and his progress was rewarded with a new deal at the region in 2014.