HIS: This Day in History: 2019 – An impeachment inquiry is initiated by the United States House of Representatives against President Donald Trump.

The impeachment inquiry against Donald Trump, the incumbent president of the United States, was initiated by House Speaker Nancy Pelosi on September 24, 2019, after a whistleblower alleged that Donald Trump may have abused the power of the presidency. Trump was accused of withholding military aid as a means of pressuring newly elected president of Ukraine Volodymyr Zelensky to pursue investigations of Joe Biden and his son Hunter and to investigate a conspiracy theory that Ukraine, not Russia, was behind interference in the 2016 presidential election. More than a week after Trump had put a hold on the previously approved aid, he made these requests in a July 25 phone call with the Ukrainian president, which the whistleblower said was intended to help Trump's reelection bid.

Believing critical military aid would be revoked, Zelensky made plans to announce investigations into the Bidens on the September 13 episode of CNN's Fareed Zakaria GPS. After Trump was told of the whistleblower complaint in late August and elements of the events had begun to leak, the aid was released on September 11 and the planned interview was cancelled. Trump declassified a non-verbatim summary of the call on September 24, the day the impeachment inquiry began. The whistleblower's complaint was given to Congress the following day and subsequently released to the public. The White House corroborated several of the allegations, including that a record of the call between Trump and Zelensky had been stored in a highly restricted system in the White House normally reserved for classified information.

In October, three congressional committees (Intelligence, Oversight, and Foreign Affairs) deposed witnesses including Ukraine ambassador Bill Taylor, Laura Cooper (the top Pentagon official overseeing Ukraine-related U.S. policy), and former White House official Fiona Hill. Witnesses testified that they believed Trump wanted Zelensky to publicly announce investigations into the Bidens and Burisma (a Ukrainian natural gas company on whose board Hunter Biden had served) and 2016 election interference. On October 8, in a letter from White House Counsel Pat Cipollone to House Speaker Pelosi, the White House officially responded that it would not cooperate with the investigation due to concerns including that there had not yet been a vote of the full House of Representatives and that interviews of witnesses were being conducted privately. On October 17, White House acting chief of staff Mick Mulvaney responded to a reporter's allegation of quid pro quo saying: "We do that all the time with foreign policy. Get over it." He walked back his comments later, asserting that there had been "absolutely no quid pro quo" and that Trump had withheld military aid to Ukraine over concerns of the country's corruption.

On October 31, the House of Representatives voted 232–196 to establish procedures for public hearings, which started on November 13. As hearings began, House Intelligence Committee Chairman Adam Schiff said Trump may have committed bribery, which is listed in Article Two as an impeachable offense. Private and public congressional testimony by twelve government witnesses in November 2019 presented evidence that Trump demanded political favors in exchange for official action. On December 10, the House Judiciary Committee unveiled their articles of impeachment: one for abuse of power and one for obstruction of Congress. Three days later, the Judiciary Committee voted along party lines (23–17) to approve both articles. On December 16, the House Judiciary Committee released a report specifying criminal bribery and wire fraud charges as part of the abuse of power charge. On December 18, the House voted mostly along party lines to impeach the president on both charges. The vote on Article One, abuse of power, was 230–197, with one vote of present. All Republicans voted against the article, joined by two Democrats. The vote on Article Two, obstruction of Congress, was 229–198, with one vote of present. All Republicans voted against the article, joined by three Democrats. Recent Republican, five-term Congressman Justin Amash of Michigan, also voted for impeachment; the frequent Trump critic had declared himself an Independent in July.