The appointment of the 55-year-old, English-born sports administrator to the new post comes after a global search was launched to find the best possible candidate for the role.
More than 100 applications were received for the position, Mr Moffett beating off four other top-class candidates on the final shortlist of five.
'I am delighted that we have uncovered such a dynamic and experienced man to take on the vital new role of Group Chief Executive at the Welsh Rugby Union,' said Glanmor Griffiths, chairman of the WRU general committee.
'We pledged to our clubs in the wake of the EGM earlier this year, when big changes were made to the constitution of our game, that we would find the right man to lead Welsh rugby into a new age both on and off the field.
'In David, who has held significant, high-ranking sporting posts in Australia, New Zealand and England, we have a man with great management skill and experience.'
The Group Chief Executive is the key appointment within the WRU Group of Companies.
When the re-organisation of the Union is completed next summer, he will be one of the 18 members of the Board of the WRU Ltd and also a member of the Board of Directors of Millennium Stadium plc.
The Group Chief Executive will also chair a new six-man WRU Executive Board which will oversee the day-to-day running of the Union's business.
The other members of the Executive Board will be the WRU Secretary, Group Finance Director, Group Marketing Director, the Director of Rugby and the Millennium Stadium Chief Executive Officer.
David Moffett - Background
Plotting the right way forward for Welsh rugby