The Cop26 meeting was set to take place at Glasgow's Scottish Events Campus - which is being turned into a temporary Covid-19 field hospital - from November 9 to 20.
But an announcement from the UN's climate body, the UNFCCC, and the UK Government said the summit would be pushed back to 2021 in light of the coronavirus pandemic.
Announcing the postponement, Cop26 president-designate and UK Business and Energy Secretary Alok Sharma said: "The world is currently facing an unprecedented global challenge and countries are rightly focusing their efforts on saving lives and fighting Covid-19.
"That is why we have decided to reschedule Cop26.
"We will continue working tirelessly with our partners to deliver the ambition needed to tackle the climate crisis and I look forward to agreeing a new date for the conference."
UN climate change chief Patricia Espinosa said: "Covid-19 is the most urgent threat facing humanity today, but we cannot forget that climate change is the biggest threat facing humanity over the long term.
"Soon, economies will restart. This is a chance for nations to recover better, to include the most vulnerable in those plans, and a chance to shape the 21st century economy in ways that are clean, green, healthy, just, safe and more resilient.
"In the meantime, we continue to support and to urge nations to significantly boost climate ambition in line with the Paris Agreement."
First Minister Nicola Sturgeon tweeted in response to the Cop26 postponement: "A disappointing decision, but absolutely the right one as we all focus on the fight against #coronavirus.
"We look forward to welcoming the world to Glasgow in 2021 #COP26."