The international convention means that EU countries now have a legal obligation to respect the rights of people with disabilities. The news has been welcomed by Euro-MP Richard Howitt.
The change is expected to call into question the practices in some central and east European countries in which people with disabilities still sometimes face the prospect of being institutionalized because of their disability.
It is the first time that European Union has signed up to an international convention in this way and the agreement itself has been concluded in record time.
Labor's Richard Howitt is the chair of the European Parliament's Intergroup on Disability Rights and has been campaigning for the EU to sign up to the UN Convention since its inception in 2001.
He said: "Today the European Union can show that it is standing four-square behind people with disabilities and their rights.
"This is about saying to people with disabilities that, wherever they live in the European Union, they are entitled to fair treatment, they have the right to make their own choices and to live their own lives.
"All future laws must now take these fundamental principles into account, from access to education through to fairness at work.
"It is good to get the principles in place, but we now have to turn warm words into action.
"Still in the European Union some people with disabilities are facing degrading and inhumane treatment. We have heard reports of people being chained to beds, of institutionalization and people being given insufficient food.
"I am proud to have campaigned for the UN Convention, but now it is in place I will not rest on my laurels.
"We must drive out these human rights abuses and ensure that people with disabilities truly win from these new legal rights."
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