Mr Morgan was elected First Secretary in February 2000 and became First Minister in October that year when the post was retitled.
Once his resignation has been accepted by HM the Queen, the Assembly will be asked to nominate a new First Minister.
Rhodri Morgan said:
“Devolution has brought many changes to Wales and its successes include free prescriptions – the simplest way of ensuring maximum benefit for patients – and free hospital parking, free bus travel for the over-60s and the highly successful new Learn through Play curriculum for children from 3 to 7 years old.
“Devolution has also allowed us to become a small, clever country, shown in the way we responded so decisively to the challenges of the recession. In one sense, the last thing I would want is to retire from office while the recession is still on.
“In another sense , the recession has caused everyone to pull together remarkably well in resisting the rising tide of unemployment, business failures and house repossessions. That is how the outstandingly successful ProAct anti-redundancy scheme was born.
“It has been a pleasure and a privilege to be First Minister and I have enjoyed it immensely. I am now looking forward to spending more time on constituency work in Cardiff West and relaxing with my ever-expanding family as well as walking the dog and digging the allotment.
“And of course I want to wish my successor all the best in the role.
“I am proud of what we have been able to achieve as a nation in the last decade, and grateful to all the people who have helped and supported me throughout that time. Most of all, it has been an honour and privilege to serve the people of Wales - diolch yn fawr i chi gyd.”
Take a look at our images from the retirement reception by visiting the Welsh Assembly Government Flickr pages.
7 December 2009