COVID-19 pandemic: Pfizer and BioNTech announced an Emergency Use Authorization application to the European Medicines Agency.
The Arecibo Telescope of the Arecibo Observatory collapses, just weeks after the announcement of its planned demolition.
COVID-19 pandemic: The United Kingdom approves Pfizer-BioNTech's BNT162b2 vaccine, being the first country in the world to do so.
Three activists in Hong Kong were jailed for their roles in the 2019–20 Hong Kong protests, with Joshua Wong getting the heaviest at 13.5 months.
December 3 – The UN Commission on Narcotic Drugs votes to remove cannabis from a list of dangerous drugs in recognition of its medical value, although some controls will remain.
COVID-19 pandemic: The number of confirmed cases of COVID-19 passes 65 million worldwide, with the global death toll exceeding 1.5 million. Figures reflect that, in the last week, over 10,000 people worldwide have died on average every day, with one death every nine seconds. According to the World Health Organization, COVID-19 had caused more deaths in 2020 than tuberculosis in 2019, as well as four times the number of deaths than malaria.
Somali Civil War: The United States announces its withdrawal from the conflict over the next month.
December 5 – COVID-19 pandemic: Russia begins mass vaccination against COVID-19 with the Sputnik V candidate.
December 6 – The 2020 Venezuelan parliamentary election takes place.
COVID-19 pandemic: The United Kingdom becomes the first nation to begin a mass inoculation campaign using a clinically authorised, fully tested vaccine, tozinameran.
A report into the 2019 Christchurch mosque shootings is released to the public.
Nepal and China officially agree on Mount Everest's actual height, which is 8,848.86m.
COVID-19 pandemic: The United States and Saudi Arabia approve tozinameran for emergency use, while Argentina approves Sputnik V.
Western Sahara conflict, Arab–Israeli conflict: Israel and Morocco normalise diplomatic relations. Simultaneously, the United States reaffirms its previous recognition of Moroccan sovereignty over the Western Sahara and announces plans to build a consulate there.
France: End of Nicolas Sarkozy corruption trial.
December 11 – The European Union agrees to reduce greenhouse gas emissions by 55% over the next decade.
COVID-19 pandemic: The number of confirmed cases of COVID-19 passes 70 million worldwide.
Bhutan and Israel normalise diplomatic relations.
COVID-19 pandemic: The United States and Canada begin mass vaccination with tozinameran.
Sudan–United States relations: The United States removes Sudan from its list of state sponsors of terrorism.
Turkey–United States relations: The United States places sanctions on Turkey in retaliation for their purchase of a S-400 missile system from Russia, making the first time they have sanctioned a NATO ally.
A total solar eclipse is visible from parts of the South Pacific Ocean, southern South America, and the South Atlantic Ocean.
December 15 – The International Criminal Court accuses the Philippines of crimes against humanity in its war on drugs.
December 16 – The United States formally designates Switzerland and Vietnam as being currency manipulators.
December 18 – COVID-19 pandemic: The number of confirmed cases of COVID-19 passes 75 million worldwide.
December 20 – COVID-19 pandemic: A highly infectious new strain of SARS-CoV-2 spreading in Europe and Australia provokes international border closures.
COVID-19 pandemic: 36 cases are reported on the Base General Bernardo O'Higgins Riquelme in the Chilean Antarctic Territory, marking the first infections in Antarctica, the last continent to report infections.
A great conjunction of Jupiter and Saturn occurs, with the two planets separated in the sky by 0.1 degrees. This is the closest conjunction between the two planets since 1623.
December 24 – The United Kingdom and the European Union agree to a comprehensive free trade agreement prior to the end of the transition period.
December 27 – COVID-19 pandemic: The number of confirmed cases of COVID-19 passes 80 million worldwide.
Famers protests in India turned violent as the farmers destroyed property and specifically targetted Reliance Jio's mobile towers.
Australia won the first test match. India's second inning turned out to be a humiliation as entire Indian team got out for mere 36 runs.
India levelled the test series with Australia winning the second test.