Donald Trump's tenure as the 45th president of the United States began with his inauguration on January 20, 2017, and ended on January 20, 2021. Trump, a Republican from New York City, took office following his Electoral College victory over Democrat nominee Hillary Clinton in the 2016 presidential election, in which he lost the popular vote to Clinton by nearly three million votes. Upon his inauguration, he became the first president in American history without prior public office or military background. Trump made an unprecedented number of false or misleading statements during his campaign and presidency. His presidency ended following his defeat in the 2020 presidential election to former Democratic vice president Joe Biden, after one term in office.

During and after his term as President of the United States, Donald Trump made tens of thousands of false or misleading claims. The Washington Post's fact-checkers documented 30,573 false or misleading claims during his presidential term, an average of about 21 per day. The Toronto Star tallied 5,276 false claims from January 2017 to June 2019, an average of 6.1 per day. Commentators and fact-checkers have described the scale of Trump's mendacity as "unprecedented" in American politics, and the consistency of falsehoods a distinctive part of his business and political identities. Scholarly analysis of Trump's tweets found "significant evidence" of an intent to deceive.