September 3
Sudanese Prime Minister Abdalla Hamdok and Abdelaziz al-Hilu, the leader of the Sudan People's Liberation Movement-North (SPLM–N), sign an agreement to transition the country into a secular state. The agreement comes three days after the signing of a peace deal between Sudan's transitional government and the Sudan Revolutionary Front, to which the SPLM–N opted out of. Weeks later on October 3, the transitional government signed a peace deal with the main rebel groups, including the Sudan People's Liberation Movement-North, which had refused to engage in previous talks.
The skeletons of 200 mammoths and 30 other animals are unearthed at a construction site for the Mexico City Santa Lucía Airport. It is the largest find of mammoth bones to date, surpassing The Mammoth Site in the U.S. which had 61 skeletons.
September 4
Pope Benedict XVI becomes the longest-lived pope at 93 years, four months, and 16 days, surpassing Pope Leo XIII, who died in 1903.
The La Línea highway tunnel, the longest road tunnel in South America at a length of 8.65 kilometres (5.37 mi), is opened in Colombia after 14 years of construction and several delays.
Kosovo and Serbia announce that they will normalize economic relations. The two countries will also move their Israeli embassies to Jerusalem, becoming the third and fourth countries to recognize Jerusalem as Israel's capital.
Bahrain and Israel agree to normalise relations, marking the fourth Israel–Arab peace deal.
September 6 – Typhoon Haishen makes landfall on Japan and then South Korea as a strong category 2-equivalent typhoon. It later makes landfall on North Korea where widespread flooding occurs.
September 14
The Royal Astronomical Society announces the detection of phosphine in Venus' atmosphere, which is known to be a strong predictor for the presence of microbial life.
The first discovery of the perfectly preserved remains of a cave bear, believed to be 22,000 to 39,500 years old (Late Pleistocene), is made in Lyakhovsky Islands, Siberia in the thawing permafrost.
September 16
A United Nations Human Rights Council fact-finding mission formally accuses the Venezuelan government of crimes against humanity, including cases of killings, torture, violence against political opposition and disappearances since 2014. President Nicolás Maduro and other senior Venezuelan officials are among those implicated in the charges.
Yoshihide Suga becomes the new Prime Minister of Japan, replacing Shinzo Abe.
September 17
France, Germany, and the United Kingdom issue a joint note verbale to the United Nations rejecting China's claims to the South China Sea, and supporting the ruling in Philippines v. China that said the historic rights per the nine-dash line ran counter to the United Nations Convention on the Law of the Sea. However the statement says that on "territorial sovereignty" they "take no position".
COVID-19 pandemic: The number of confirmed cases of COVID-19 passes 30 million worldwide.
September 19 – A 1634 edition of The Two Noble Kinsmen, the last play by English playwright William Shakespeare, is discovered at the Royal Scots College's library in Salamanca, Spain. It is believed to be the oldest copy of any of his works in the country.
September 20 – BuzzFeed News and the International Consortium of Investigative Journalists (ICIJ) release the FinCEN Files, a collection of 2,657 documents relating to the Financial Crimes Enforcement Network describing over 200,000 suspicious transactions valued at over US$2 trillion that occurred from 1999 to 2017 across multiple global financial institutions.
September 21 – Microsoft agrees to buy video game holding company ZeniMax Media, including Bethesda Softworks and their following subsidiaries for US$7.5 billion, in what is the biggest and most expensive takeover in the history of the video game industry.
September 27 – Deadly clashes erupt in Nagorno-Karabakh between Armenian and Azerbaijani forces. Armenia, Azerbaijan, and the Republic of Artsakh introduce martial law and mobilize forces.
September 29
COVID-19 pandemic: The worldwide death toll from COVID-19 exceeds one million.
The Emir of Kuwait Sheikh Sabah al-Sabah dies at the age of 91. Crown Prince Nawaf Al-Ahmad Al-Jaber Al-Sabah is named his successor.
India
14 September - Three Bills on agriculture reforms are introduced in the Parliament to replace the ordinances issued during the lockdown on June 5.
30 September - The court acquitted all the 32 accused of the Demolition of the Babri Masjid struture including L.K Advani, Murli Manohar Joshi, Uma Bharti, Vinay Katiyar and several others in the case on account of inconclusive evidence. The special court judge said "“The demolition was not pre-planned.”
