The WRU immediately announced a world-wide search for a new Head Coach and a full review of the elite game in Wales has also been launched.
The full coaching team were informed of Gareth Jenkins's departure and will now also contribute in the rugby review.
All the Welsh players from the squad were then addressed by Roger Lewis and Gareth Jenkins and informed of the Head Coach's departure shortly before they left their base at Pornichet in Brittany to fly home to Wales.
A meeting of the full board of the WRU will be held on Tuesday to discuss the global search for a replacement and details of the elite rugby review.
WRU Group Chief Executive Roger Lewis said: "No-one can deny the total commitment, passion and dedication that Gareth Jenkins has delivered to Welsh rugby.
"He lives and breathes rugby and I want to thank him for everything he has done and the incredible amount of hard work he has put in.
"We have spoken at length about his departure and he has behaved with great dignity. He is a proud man who loves the game and behaves honourably at all times.
"Sport at this level is defined by success and the reality is that Wales have failed in their bid to reach the quarter-final stage.
"We have now started a world-wide search for a new head coach and I can assure the people of Wales we will appoint the best person for the role.
"The review now underway will include input from the players and coaches, including Gareth Jenkins, plus everyone involved in the elite game in Wales because we need to fully understand why we have reached this point.
"Today the journey has started for Wales to the 2011 Rugby World Cup and we must aim for one thing, and that is the success of a winning Wales."
WRU Chairman David Pickering added: "We want to thank Gareth Jenkins personally for the tremendous effort he has made on behalf of the nation.
"Unfortunately we have fallen short of our aims in this Rugby World Cup and we have acted decisively and quickly. The worst thing now would have been a period of indecisiveness. It is time for us to turn our focus directly on the future."
Gareth Jenkins said: "I accept and understand the decision that has been taken and I leave the post with sadness but no regrets.
"I have worked with a tremendous team of coaches, administrators and players and I leave in the full knowledge that we have given it our all."