The 2000s (pronounced "two-thousands"; shortened to the '00s and known as the aughts or noughties) was a decade that began on January 1, 2000, and ended on December 31, 2009.

The early part of the decade saw the long predicted breakthrough of economic giants in Asia, like India and China, which had double-digit growth during nearly the whole decade. It is also benefited from an economic boom, which saw the two most populous countries becoming an increasingly dominant economic force. The rapid catching-up of emerging economies with developed countries sparked some protectionist tensions during the period and was partly responsible for an increase in energy and food prices at the end of the decade. The economic developments in the latter third of the decade were dominated by a worldwide economic downturn, which started with the crisis in housing and credit in the United States in late 2007 and led to the bankruptcy of major banks and other financial institutions. The outbreak of this global financial crisis sparked a global recession, beginning in the United States and affecting most of the industrialized world.

The decade saw the rise of internet, which grew from covering 6.7% to 25.7% of the world population. This contributed to globalization during the decade, which allowed faster communication among people around the world; social networking sites arose as a new way for people to stay in touch from distant locations, as long as they had an internet connection. Myspace was the most popular social networking website until June 2009, when Facebook overtook it in number of American users. E-mail continued to be popular throughout the decade and began to replace "snail mail" as the primary way of sending letters and other messages to people in distant locations, though it had existed since 1971. Google, YouTube, Ask.com and Wikipedia emerged to become among the top 10 most popular websites. Amazon overtook eBay as the most-visited e-commerce site in 2008. AOL significantly declined in popularity throughout the decade, falling from being the most popular website to no longer being within the top 10. Excite and Lycos fell outside the top 10, and MSN fell from the second to sixth most popular site, though it quadrupled its monthly visits. Yahoo maintained relatively stable popularity, remaining the most popular website for most of the decade.

The war on terror and War in Afghanistan began after the September 11 attacks in 2001. The International Criminal Court was formed in 2002. In 2003, a United States-led coalition invaded Iraq, and the Iraq War led to the end of Saddam Hussein's rule as Iraqi President and the Ba'ath Party in Iraq. Al-Qaeda and affiliated Islamist militant groups performed terrorist acts throughout the decade. The Second Congo War, the deadliest conflict since World War II, ended in July 2003. Further wars that ended included the Algerian Civil War, the Angolan Civil War, the Sierra Leone Civil War, the Second Liberian Civil War, the Nepalese Civil War, and the Sri Lankan Civil War. Wars that began included the conflict in the Niger Delta, the Houthi insurgency in Yemen, and the Mexican Drug War.

Climate change and global warming became common concerns in the 2000s. Prediction tools made significant progress during the decade, UN-sponsored organizations such as the IPCC gained influence, and studies such as the Stern report influenced public support for paying the political and economic costs of countering climate change. The global temperature kept climbing during the decade. In December 2009, the World Meteorological Organization (WMO) announced that the 2000s may have been the warmest decade since records began in 1850, with four of the five warmest years since 1850 having occurred in this decade. The WMO's findings were later echoed by the NASA and the NOAA. Major natural disasters included Cyclone Nargis in 2008 and earthquakes in Pakistan and China in 2005 and 2008, respectively. The deadliest natural disaster and most powerful earthquake of the 21st century occurred in 2004 when a 9.1–9.3 M_w earthquake and its subsequent tsunami struck multiple nations in the Indian Ocean, killing 230,000 people.

Usage of computer-generated imagery became more widespread in films produced during the 2000s, especially with the success of 2001's Shrek. Anime films gained more exposure outside Japan with the release of Spirited Away. December 2009's Avatar became the highest-grossing film. Documentary and mockumentary films, such as March of the Penguins, Super Size Me, Borat and Surf's Up, were popular in the 2000s. 2004's Fahrenheit 9/11 by Michael Moore was the highest grossing documentary of all time. Online films became popular, and conversion to digital cinema started. Video game consoles released in this decade included the PlayStation 2, the Xbox, the GameCube, the Wii, the PlayStation 3 and the Xbox 360; while portable video game consoles included Game Boy Advance, Nintendo DS and PlayStation Portable. Wii Sports was the decade's best-selling console video game, while New Super Mario Bros. was the decade's best-selling portable video game. J. K. Rowling was the best-selling author in the decade overall thanks to the Harry Potter book series, although she did not pen the best-selling individual book, being second to The Da Vinci Code. Eminem was named the music artist of the decade by Billboard.

During this decade, the world population grew from 6.1 to 6.9 billion people. Approximately 1.35 billion people were born, and 550 million people died.