This was published under the 2010 to 2015 Conservative and Liberal Democrat coalition government
A ceremony took place ahead of the march at Ynysangharad War Memorial Park in Pontypridd at 11am, followed by the parade through Pontypridd town centre.
Many turned out on the streets to welcome the regiment and Pontypridd town centre came to a standstill as the soldiers marched past.
More than 200 soldiers, many of whom have recently returned from Afghanistan on Operation Herrick 16, took part in the parade, led by the Band of the Welsh Guards.
On its latest tour of duty in Afghanistan the battalion conducted a wide range of roles in Helmand province, focusing on the continuing training, development and mentorship of the Afghan police force in particular.
However, success was not achieved without sacrifice, with Lance Corporal Lee Davies, Guardsman Craig Roderick, Guardsman Apete Tuisovurua and Warrant Officer Class 2 Leonard Thomas all killed in action.
Mayor of Rhondda Cynon Taf, Councillor Doug Williams, said:
We are both proud and honoured to bestow this wonderful accolade on a regiment which is held in such high esteem and with strong links to our county borough.
The Freedom of the County Borough, bestowed by Rhondda Cynon Taf Council, is the highest civic honour a local authority can bestow and is only ever presented to distinguished individuals and groups.
Past recipients include the award-winning author and playwright Dr Elaine Morgan, the South Wales Miners, tenor Stuart Burrows and the Royal Welsh regiment.