The Senate, run by the president's fellow Republicans, voted to acquit him 52-48 on charges of abuse of power and 53-47 on obstruction of Congress.
Democrats charged Mr Trump in December with pressuring Ukraine to smear a potential White House rival.
He will now become the first impeached president to seek re-election.
Impeachment allows Congress - the part of the US government that writes and brings in laws - to put presidents on trial.
It is a rare event and a political process, rather than a criminal one.
Watch: What does it take to impeach a president?
In its historic vote on Wednesday, the Senate decided not to remove America's 45th president from office on charges arising from his dealings with Ukraine.
If convicted on either charge, Mr Trump would have had to turn over his office to Vice-President Mike Pence.
The Democratic-led House of Representatives approved the articles of impeachment on 18 December.
How did President Trump react?
Mr Trump, who is seeking a second four-year term in the 3 November election, always denied wrongdoing.
His re-election campaign said in a statement: "President Trump has been totally vindicated and it's now time to get back to the business of the American people.
"The do-nothing Democrats know they can't beat him, so they had to impeach him." It said "this terrible ordeal" and "nonsense" was merely a Democratic campaign tactic.
The statement added: "This impeachment hoax will go down as the worst miscalculation in American political history."
Mr Trump - whose personal approval rating with American voters hit a personal best of 49% this week, according to Gallup - tweeted that he would speak on Thursday about the case.
How did the impeachment vote play out?
Mitt Romney of Utah was the only Republican senator to cross the aisle and convict Mr Trump, on the first charge of abuse of power.
Despite Democratic hopes, two other moderate Republicans, Susan Collins of Maine and Lisa Murkowski of Alaska, did not join Mr Romney in voting to convict the president.
Some Republican senators criticised Mr Trump's behaviour in recent days, but said it did not rise to the level of impeachment.
Three centrist Democratic senators who Republicans had hoped would side with them instead voted to convict Mr Trump.
They were Kyrsten Sinema of Arizona, Joe Manchin of West Virginia and Doug Jones of Alabama.
A two-thirds majority vote was needed to remove Mr Trump, which was always going to be a long shot in a 100-seat chamber controlled by his party.
How might Mr Trump's acquittal shape the 2020 race for the White House?
According to polls, the nation's political disposition is much as it was before the impeachment process began. The US is sharply divided along partisan lines.
This result, though, will energise the president's campaign blueprint to rally his Republican base to support him in November.
The political strategy for the White House at this point is clear: to paint impeachment as just another example of a Washington establishment that has been out to get the president - and, by connection, those who support him - from the beginning.
Democrats, meanwhile, got the impeachment that they wanted - a black mark on his presidency - if not the result that they had hoped for.
Read more of Anthony Zurcher's analysis
What was Trump accused of?
The impeachment charges focused on Mr Trump's request that Kyiv announce a corruption investigation into Joe Biden, a Democratic White House candidate, and his son Hunter Biden.
Mr Trump has argued that the younger Biden improperly held a board position with a Ukrainian natural gas firm while his father was US vice-president and in charge of American-Ukrainian relations.
Democrats accused Mr Trump of abusing his power by withholding $391m (£300m) in security aid to prod Ukraine's president into digging up dirt on the Bidens.
Who's who in Trump-Ukraine saga
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They also charged Mr Trump with obstruction of Congress after the White House blocked testimony and documents sought by the House impeachment investigators.
The impeachment inquiry stemmed from Mr Trump's phone call on 25 July 2019 in which he asked Ukraine's President Volodymyr Zelensky to "do us a favour".
Following a complaint from an anonymous government whistleblower, Democrats launched their investigation in September, compiling a 28,000-page report.
What is the historical precedent?
Mr Trump is the third US president to have been impeached.
The two others, Bill Clinton in 1999 and Andrew Johnson in 1868, were left in power by the Senate and did not seek re-election.
President Richard Nixon resigned before he could be impeached.
How did Democrats react?
Democrats expressed concern that acquittal would further embolden a president whom they depict as a demagogue.
House Speaker Nancy Pelosi said Mr Trump remains "an ongoing threat to American democracy" and that Senate Republicans had "normalised lawlessness"
Senate Democratic leader Chuck Schumer said there will always be "a giant asterisk next to the president's acquittal"
"No doubt, the president will boast he received total exoneration," said the New York senator. "But we know better."
What did Republican senators say?
Senator Lamar Alexander of Tennessee warned before he voted to acquit that a guilty verdict would "rip the country apart"
Senate Republican leader Mitch McConnell said the entire case against Mr Trump had been a "circus" and "a colossal political mistake"
Lindsey Graham of South Carolina said the proceedings were a "sham" designed to destroy a presidency
Mr Romney, the 2012 Republican presidential nominee, choked up on the Senate floor as he explained his decision to convict the president
He said Mr Trump had been "guilty of an appalling abuse of public trust" and "a flagrant assault on our electoral rights, our national security and our fundamental values".
Is this the end of the matter?
Mr Trump has probably not heard the last of the Ukraine investigation.
Jerry Nadler, the Democratic chairman of the House Judiciary Committee, said on Wednesday the chamber would "likely" issue a subpoena to Mr Trump's former National Security Adviser, John Bolton.
Senate Republicans ultimately declined to seek Mr Bolton's testimony during the president's impeachment trial, provoking uproar from Democrats.
A manuscript of a forthcoming Bolton memoir reportedly alleges Mr Trump told his former national security adviser to help him pressure Ukraine.