The WRU will now launch a worldwide search for a replacement.
The rest of the Wales coaching staff - Nigel Davies, Neil Jenkins and Rowland Phillips - will have their positions reviewed by the WRU.
But Jenkins has paid the price for Wales' failure to reach the World Cup quarter-finals. They were knocked out of the tournament following a 38-34 defeat by Fiji.
Jenkins, who was contracted until the end of the 2008 RBS 6 Nations, insisted after the match he would not resign from his post and urged against "panic" and "knee-jerk" reactions.
But the WRU board met in Nantes and felt they had no option but to act quickly and decisively.
Lewis and Pickering travelled down from Nantes to the team base in Pornichet this morning and informed Jenkins of the decision in a private meeting.
They then met with the coaching staff before informing the Wales players of the decision.
Jenkins was only in the job for 16 months - but he presided over Wales' worst World Cup performance in the professional era and leaves having won just six of 20 Tests in charge.
Lewis and Pickering are set to explain the decision and outline their plans for finding a replacement at a press conference at the Vale of Glamorgan.
The hunt for a replacement head coach begins immediately - as do preparations for the 2011 World Cup.
Lewis and Pickering are determined Wales must get the right man for the job, whatever nationality.
It is a bitter blow for Jenkins, whose ambition throughout a stellar 20-year coaching career with Llanelli was to take charge of the national team.
Jenkins had been the obvious choice and clear favourite when he took over from caretaker coach Scott Johnson in the spring of 2006.
Given a relatively short run-up, his plan was to focus everything on building for the World Cup.
Jenkins began the year by declaring his vision for Wales winning the World Cup 'the Welsh way' and he was convinced his side could at the very least emulate the achievements of the 1987 team that finished third.
But those ambitions were gradually scaled down as the results failed to materialise and the pressure began to rise.
Cracks began to appear over tactics during the World Cup, with senior players questioning Wales' approach following the defeat to Australia.
Jenkins appeared a man under huge pressure on the eve of the Fiji game. He took a huge amount of criticism from sections of the press and refused to talk to one Welsh newspaper throughout the tournament.