Sir Wyn Williams (61) will formally take up the appointment at the first meeting of the PRGB due to be held later this month.
The post does not receive any remuneration and Sir Wyn will attend the monthly PRGB meetings at times which do not conflict with his judicial duties.
Sir Wyn is a Presiding Judge for the Wales Circuit, was appointed a Specialist Chancery Judge for Wales in 2004, became a Bencher of the Inner Temple in 2007, took Silk in 1992 and was originally called to the Bar in 1974. He is also the Deputy Chairman for the Boundary Commission for Wales.
He was born in the Rhondda Valley, where he still lives, and is a former player, Chairman and remains a Trustee for life of Tylorstown RFC. Sir Wyn is an avid supporter of rugby at all levels in Wales.
The Group Chief Executive of the Welsh Rugby Union, Roger Lewis, said: "We are delighted to announce the appointment of someone of Sir Wyn's calibre as the inaugural chair of the PRGB.
"His status as a High Court judge ensures he takes on this post with a formidable reputation for objectivity, fairness and an undoubted ability to find intelligent solutions to complex problems.
"His interest in rugby and true understanding of the game at all levels means he brings to the role a real knowledge of the issues which the PRGB will prioritise.
"As a High Court judge with a well-deserved reputation of national standing, Sir Wyn has all the qualities necessary to prove an ideal independent chair of the PRGB."
Speaking on behalf of the four Regions, Scarlets Chief Executive, Mark Davies, added: "The scale, scope and role of the new PRGB and the clear aims that we have set out mean that we need a very considerable individual indeed to be able to share the responsibility and lead the discussions that result in us collectively achieving our objectives for a healthy and sustainable future for Welsh rugby.
"Sir Wyn Williams' lifelong contribution to grassroots rugby and his firm belief that the best structures are built on strong foundations will be a tremendous asset to PRGB and Welsh rugby as a whole.
"His knowledge and passion for Welsh rugby, together with the scale and degree of judgement he employs daily at a very profound level, means it's a role clearly well within his capability and experience. I'm sure he will facilitate our discussions at PRGB in a clear and constructive manner and encourage a real spirit of unity, vision and purpose."