The 21st century is the current century of the Anno Domini era, in accordance with the Gregorian calendar. It began on January 1, 2001 and will end on December 31, 2100. It is the first century of the 3rd millennium. It is distinct from the time span known as the 2000s, which began on January 1, 2000 and will end on December 31, 2099.
- The twenty-first century will be the American century... [T]he twenty-first century truly began on September 11, 2001, ten years later, when planes slammed into the World Trade Center and the Pentagon... Al Qaeda has failed in its goals. The United States has succeeded, not so much in winning the war as in preventing the Islamists from winning, and, from a geopolitical perspective, that is good enough... The twenty-first century has begun with an American success that on the surface looks like not only a deafeat but a deep political and moral embarrassment.
- George Friedman, The Next 100 Years: A Forecast for the 21st Century (2009), p. 18, Doubleday
- [D]isequilibrium will dominate the twenty-first century, as will efforts to contain the United States. It will be a dangerous century, particularly for the rest of the world.
- George Friedman, The Next 100 Years: A Forecast for the 21st Century (2009), p. 47, Doubleday
- Old institutions have shattered, but new ones have not yet emerged. The twenty-first century will be a period in which a range of new institutions, moral systems, and practices will begin their first tentative emergence. The first half of the twenty-first century will be marked by intense social conflict globally. All of this frames the international struggles of the twenty-first century.
- George Friedman, The Next 100 Years: A Forecast for the 21st Century (2009), p. 64, Doubleday
- When I was growing up in the 1950s, the twenty-first century was an idea associated with science fiction, not a reality in which I would live. Practical people focus on the next moment and leave the centuries to dreamers. But the truth is that the twenty-first century has turned out to be a very practical concern to me. I will spent a good deal of my life in it.
- George Friedman, The Next 100 Years: A Forecast for the 21st Century (2009), p. 254, Doubleday
- Dear friends, Let’s be clear: human activities are at the root of our descent towards chaos. But that means human action can help solve it. Making peace with nature is the defining task of the 21st century. It must be the top, top priority for everyone, everywhere.
- António Guterres, "The State of the Planet," (2 December 2020), as quoted in Vital Speeches of the Day, 87(2), pp. 40–44.
- Hopelessness is becoming the hallmark of the 21st century.
- We are witnessing the rise of what I call "a fragmented globality." World histories and local histories are at once becoming both increasingly intertwined and increasingly contradictory. The twenty-first century is likely to be marked by the speed and brutality of these contradictions.
- Encyclopedic article on 21st century at Wikipedia