He takes up the post with immediate effect and will also represent the WRU on a number of key committees.
The Board voted for the new chairman in a secret ballot after both Gareth Davies and current Board director Martin Davies were nominated as candidates for the position.
In a further vote by the Board Ken Hewitt was elected to continue as Deputy Chairman of the WRU.
Appointments to a number of key committees will be confirmed at a future meeting of the full WRU Board.
Gareth Davies told the Board he will be informing his current employers he will be terminating his contract as Chief Executive of the Newport Gwent Dragons after a suitable notice period to avoid any conflict of interest in his new role.
He said: “It is a fantastic honour to be elected Chairman of the WRU and I will aim to live up to my old Gwendraeth School motto which is : “There is no honour without responsibility.”
“I want to thank the Board of Directors for their support and confidence in my ability to represent the WRU in this prodigious role. I have also been encouraged by the support I have already received from so many grassroots clubs.
“I also want to personally thank the departing Chairman, David Pickering, for the immense contribution he has made across the past eleven years he held this post.
“We must continue to evolve and develop to seize the opportunities and meet the challenges ahead and I am determined to ensure the WRU is a governing body we can be proud of.
“I look forward to working with my colleagues on the Board, the Executive and staff of the WRU and everyone involved in our sport to ensure we build on the success of recent years.”
The Group Chief Executive of the WRU, Roger Lewis, said: “I want to offer my congratulations to Gareth on his appointment to the role of Chairman of the Welsh Rugby Union.
“We all know how important the Chairman of the WRU is in Wales, not just for our sport, but for the position rugby holds within the cultural life of our nation.
“I look forward to working closely with Gareth as we seek to sustain and develop our role as the national sport of Wales and a key nation at the top level of the world game.
“Our business is in good shape, our international status is strong and our focus on the community game is paying dividends in strengthening the infrastructure of our sport at the grassroots level.
“We can’t take our foot off the pedal and there are exciting times ahead for all of us involved in Welsh rugby.
“I also want to personally thank our departing Chairman David Pickering for everything he has achieved for our game during his term in the role and wish him well for the future away from the Board.”
At the Board meeting today, new district directors Chris Morgan, David Young and national directors, Anthony Buchanan and Gareth Davies all took up their appointments.
They replace Aurwel Morgan and Roy Giddings on districts D and B, the national director Gerald Davies who has stepped down and David Pickering who was not relected for a further term.