The Prince of Wales has renovated a farmhouse within a few miles of the rugby club, known as Llywnywermod estate near the village of Myddfai, which he uses as his official residence when he is in the country.
Davies and members of the Llandovery club initially broached the subject of establishing a link with the Prince when invited to visit the house with a variety of other local personalities and dignitaries after Charles and Camilla, Duchess of Cornwall, took up residence at the property in June 2008.
But it was only when the Prince returned to the club late last month that Davies learned his request had met with approval.
"It was a great honour to be invited to the Prince's residence in Wales in the first place and he was so welcoming and accommodating when I met him that it just seemed natural to me to come right out and ask him," said Davies.
"He said we should write to him, but we certainly didn't expect him to respond in this way during a personal visit and we have been overwhelmed by the good news.
"Llandovery rugby club has a long and proud history in the game, we formed in 1878 and became one of the founder members of the Welsh Rugby Union three years later.
"News of the Prince's royal patronage has created a real buzz about the place and lifted everyone for the season ahead.
"Prince Charles spent hours talking to each and every member of the club on his visit, walking up and down lines and lines of our different age group teams. He unveiled a plaque to officially open our new terrace and to hear he was willing to become an official patron was just the icing on the cake for us.
"The club is the real heart of the community here and to be able to claim association with the Prince, and to be the only club in Wales who can do so, is a boost to everyone in Llandovery."
Her Majesty Queen Elizabeth II is the official patron of the Welsh Rugby Union and Prince William became the Vice Royal Patron of the WRU in February 2007.
The Prince of Wales himself is a patron of the London Welsh club, but this is his first association with a club in Wales.
"The Prince of Wales is delighted to become the Royal Patron of Llandovery Rugby Club," added a Clarence House spokesman.
"He thoroughly enjoyed his recent visit and has been particularly impressed by the many ways in which the club works with and in the local community,"
Llandovery was represented at the inaugural meeting of the WRU at Castle Hotel, Neath on 12 March 1881 by Charles Prytherch Lewis.
Lewis captained Wales to their first ever victory, their second international match which was against Ireland, at Lansdowne Road, Dublin.
A side showing eleven changes, including captain, to the loss in the first official Wales international - which was against England - beat Ireland by two goals and two tries to nil,
The other clubs represented on that historic occasion in 1881 when the WRU was formed were: Bangor, Brecon, Cardiff, Lampeter, Llanelli, Llandeilo, Merthyr, Newport, Pontypool and Swansea.