A portreeve is the title of a powerful official in Wales possessing political or administrative authority over a town.

By the late Middle Ages portreeves acted as representatives of the people to ensure that their duties to the mayor and community were fulfilled. In some cases the role has been combined with that of mayor. 

Other duties of the Portreeve in Llantrisant were to summon and attend the Court Leet and to receive the fees on the admission of Freemen.

The oath of the Portreeves of Llantrisant were: 

“I do solemnly and sincerely in the presence of God, profess, testify and declare upon the true faith of a Christian, that I will never exercise any power, authority or influence which I may possess by virtue of the office of Portreeve of the Borough of Llantrisant, to injure or weaken the Protestant Church, as it is by law established in England.

"Or to disturb the said Church, or the Bishops and Clergy of the said Church in the possession of any rights or privileges to which such Church or the said Bishops and Clergy are, or may be by law entitled”.

The last Portreeve of Llantrisant was John Evans in 1880. He became a Trustee of the new Llantrisant Town Trust when it was formed in 1889.