Mr Trump was giving a speech to supporters in Butler, Pennsylvania when the incident occurred.
He was seen ducking to the ground clutching his ear as a series of shots rang out and people screamed in panic.
Secret Service agents dashed up to aid the former president, who was bundled into an armoured vehicle and driven away from the scene.
Here is all we know about the attempted assassination of Donald Trump so far.
What we know about the Donald Trump assassination attempt
What actually happened?
As stated above Mr Trump was giving a speech at a campaign rally in Pennsylvania when shots rang out.
Secret Service agents then rushed onto the stage and surrounded the former president.
Mr Trump was then driven away from the scene and could be seen to be bleeding from his ear.
One person in the crowd was killed and two were critically injured.
Is Donald Trump hurt?
Mr Trump confirmed he had been shot but not seriously hurt as he said a bullet pierced the upper part of his right ear.
FULL INTERVIEW with a witness, talking to @BBCNews, who says he saw a man with a gun on a building roof firing shots.
Donald Trump was rushed off stage during a rally in Pennsylvania after gun shots were heard.
He talked to @BBCBlindGazza – more information @BBCNews pic.twitter.com/aWqSXbzor2
— BBC Newsnight (@BBCNewsnight) July 14, 2024
Who is the gunman?
The FBI has identified the gunman as Thomas Matthew Crooks, a 20-year-old man from Pennsylvania.
Crooks was shot by police on the scene and is believed to have climbed onto the roof of a shed outside the rally before discharging an AR-style rifle, The Telegraph reports.
He was a registered Republican, the Associated Press reported.
What has Donald Trump said on the incident?
Writing on his Truth Social platform, Mr Trump said he was “shot with a bullet that pierced the upper part of my right ear”.
He said: “I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin,” he said on social media.
“Much bleeding took place, so I realised then what was happening.”
He added: “I want to thank The United States Secret Service, and all of law enforcement, for their rapid response.”
Extending condolences to the families of the other casualties, he said: “It is incredible that such an act can take place in our country.”
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How has the world reacted?
Leaders around the world have condemned the attempted assassination of Mr Trump, with current President Jo Biden calling the attack “sick”.
Mr Biden spoke with Trump on Saturday evening, the White House said.
Meanwhile, Prime Minister Sir Keir Starmer said he was “appalled by the shocking scenes”.
He added: “Political violence in any form has no place in our societies and my thoughts are with all the victims of this attack.”
