Elinor Ostrom has become the first woman to win the Nobel Prize for economics since it began in 1968.
Ms Ostrom won the prize with fellow American Oliver Williamson for their separate work in economic governance.
The Royal Swedish Academy of Sciences cited Professor Ostrom, who teaches at Indiana University, "for her analysis of economic governance," saying her work had demonstrated how common property could be successfully managed by groups using it.
BBC News website readers have been sending their reaction to this decision.
I think she deserves that prize. Her analysis of the situation and her contribution are quite outstanding. She opens the way for all female economists.
Jacques Tshimanga Tshindaye, Lusaka, Zambia
I am familiar with Elinor Ostrom's excellent work on the topic of governance of the commons. I found her observations very insightful and pragmatic when writing my LLM thesis on the law of the sea. Good on her for winning this prestigious award, and particularly as the first woman ever to do so.
Anshuman Chakraborty, Wellington, New Zealand
Professor Elinor Ostrom's selection as 2009 Nobel Prize winner in economic science is the greatest news. Even I, an individual living and working in Nepal, feel a sense of fulfilment at the news. I had a chance to work with her on some irrigation performance management and development of a bottom-up information system integrating communities. She had very keen ears to listen to people, very keen eyes to observe, and very humane and friendly ways to respond to the people. She was very keen on understanding how local farmers and user groups devise rules to govern their use of the local natural resources. That opportunity to work with her provided such a sea of learning experience that the UN was able to develop a very useful flagship development programme linking people, institutions, and local governance.
Indra Sharan KC, Pawai Gamde, Syangja, Nepal
Excellent work created by a woman, who is outstanding in her academic field. A great job always depends on hardwork and enthusiasm. Elinor Ostrom is a shining Nobel winner.
Jin Yu, Shanghai, China
I think that it's a step forward and I'm proud the society choose a woman.
Kevin Hulmes, Adelaide, South Australia
Yes, I think she deserves this award. It is quite a coincidence that I have just finished one of her books "Governing the Commons", and while I was reading it, I did wonder whether a lot of people had read the book. It is quite evident that she has worked very hard in addressing the problem of managing the "Common Pool Resources". Although the scenario has changed from what it used to be, her comments and opinions are still relevant and will always hold true for time to come as there will always be conflicts in managing the Common Pool Resources.
Divya Gupta, Columbus, Ohio, USA
I believe that awarding the Nobel Prize in economics to Elinor Ostrom is recognition of a powerful alternative view in economics. If people can order their economies in sustainable ways with little help from the experts, which is what Ostrom demonstrates, then we have an alternative and the world is saved!
Peter Knight, Dunedin, New Zealand
It is surprising that economic Noble Prizes are awarded for "theories". Have their theories been subjected to practical situations and proven to be correct? Even Einstein could not win a Noble Prize for his theory of relativity, so the question arises as to why should economists be awarded a prize for a theory?
Sid, Delhi, India
I am glad that an American woman has won the prestigious Nobel Prize in economics at last. So, I would like to congratulate Ms Ostrom on her win.
Jampel Norbu, USA
Given that the USA was "prime suspect" in the on-going global recession, it is strange that, once again, an American wins the Nobel Prize for economics. However, this is in keeping with awarding Barack Obama the Nobel Peace Prize.
Tony Storey, Sudbury, Canada
I'm not familiar with her work but I hope it helps developing countries and doesn't move them further into poverty.
Albet Akhidenor, Ile-Ife, Nigeria
While I think it's fabulous that a woman "finally" won the Nobel Prize for economics, it says a lot about how women were actively discouraged (by who else? males!) from pursuing PHDs in economics.
Dr Saku Gunasegaram, Venice, Italy
Congratulation to Prof Elinor Ostrom for winning the economics Nobel Prize! It is great news for me and my family. I worked under her guidance at Indiana University and in Nepal from 1996 to 1998 analysing governance systems and institutional arrangements in common property resource, particularly forest resource management. Her continued interest and guidance on governance structures managing forests in the ecologically critical Nepal Himalaya will always be praised and remembered. Her contribution to safeguard forests in Nepal through alternative governance systems is great.
Shree G Shah, PhD, Kathmandu, Nepal