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.

The environmental policy of the Donald Trump administration represented a shift from the policy priorities and goals of the preceding Barack Obama administration. Where President Obama's environmental agenda prioritized the reduction of carbon emissions through the use of renewable energy with the goal of conserving the environment for future generations, the Trump administration policy was for the US to attain energy independence based on fossil fuel use and to rescind many environmental regulations. By the end of Trump's term, his administration had rolled back 98 environmental rules and regulations, leaving an additional 14 rollbacks still in progress. As of early 2021, the Biden administration was making a public accounting of regulatory decisions under the Trump administration that had been influenced by politics rather than science.