In Pictures: Four years of President Donald J Trump

During his inauguration speech on this day in 2017, Donald Trump said that he was taking "an oath of allegiance to all Americans".

Four years later, he is leaving office as the first US president to be impeached twice, with a trial due in the Senate in the coming weeks.

Mr Trump's first term in office came during a time of political polarisation across America and dysfunction in Washington DC, making his presidency among the most contentious in US history.

He curtailed immigration, abandoned international treaties, alienated longtime US allies, praised authoritarian foreign leaders, exhibited deference to longtime American adversary Russia, secured deep tax cuts that especially benefited the rich and corporations and vilified opposition Democrats.

Mr Trump led a disjointed US government response to the 2020 coronavirus pandemic - downplaying its seriousness, casting doubt on protective masks and predicting the pathogen's miraculous disappearance - that many medical experts said worsened the public health crisis and cost lives.

This gallery looks back at some of the many memorable moments of a former reality television star who became the 45th President of the United States.

There will be special coverage of the US Presidential Inauguration on RTÉ One at 3.30pm