The Nobel Peace Prize has been awarded to the International Campaign to Abolish Nuclear Weapons (ICAN).
Berit Reiss-Andersen, the Nobel committee chair, said it was due to the group's "groundbreaking efforts to achieve a treaty prohibition" on nuclear weapons.
"We live in a world where the risk of nuclear weapons being used is greater than it has been for a long time," she continued.
In a statement on the win, ICAN stated: 'This prize is a tribute to the tireless efforts of many millions of campaigners and concerned citizens worldwide who, ever since the dawn of the atomic age, have loudly protested nuclear weapons, insisting that they can serve no legitimate purpose and must be forever banished from the face of our earth.'
In July, after pressure from ICAN, 122 nations backed a UN treaty designed to ban and eventually eliminate all nuclear weapons. But none of the nine known nuclear powers in the world - including the UK and the US - endorsed it.
ICAN, a coalition of hundreds of non-governmental organisations (NGOs), is 10 years old and is based in Geneva, Switzerland. The group will receive nine million Swedish kronor ($1.1 million, £846,000) along with a medal and a diploma at a ceremony in December.
Beatrice Fihn, executive director of the group, told reporters that the prize had come as a surprise but that it was "a huge signal" that the group's work was "needed and appreciated".
"The laws of war say that we can't target civilians. Nuclear weapons are meant to target civilians; they're meant to wipe out entire cities," she said, adding: "That's unacceptable and nuclear weapons no longer get an excuse.
"It's a giant radioactive bomb, it just causes chaos and havoc and civilian casualties. It is not a weapon that you can use in line with the laws of war.
"Every state matters here. The more states that sign and ratify this treaty the stronger the norm is going to get. They're not moving towards disarmament fast enough."
a coalition group supported by hundreds of non-governmental organisations (NGOs) in over 100 countries across the world (including CND)
formed in 2007, inspired by a similar campaign to ban the use of landmines worldwide
- supporters include actor Michael Sheen, artist Ai Weiwei and former UN Secretary-General Ban Ki-moon
- its lobbying encouraged the UN to adopt the Treaty on the Prohibition of Nuclear Weapons earlier this year which has been signed by 53 countries so far