Donald John Trump Jr. (born December 31, 1977), often nicknamed Don Jr., is an American businessman and activist. He is the eldest child of Donald Trump, the 45th and 47th president of the United States, and his first wife, Ivana Trump.

Trump serves as a trustee and executive vice president of the Trump Organization, running the company alongside his younger brother Eric. During their father's first presidency, the brothers continued to engage in deals and investments in foreign countries and collect payments at their U.S. properties from foreign governments, despite pledging not to do so. He also served as a boardroom judge on the reality TV show featuring his father, The Apprentice. In addition, he authored Triggered in 2019 and Liberal Privilege in 2020.

Trump was active in his father's 2016 presidential campaign. He cooperated with Russia in their interference in the 2016 United States elections and had a meeting with a Russian lawyer who promised damaging information about the campaign of Hillary Clinton in the 2016 presidential election. Trump campaigned for several Republicans during the 2018 midterm elections.

Trump was also active in his father's 2020 presidential campaign, often on the campaign trail and featured in the news for making unfounded claims. During the election, he called for "total war" as the results were counted and promoted the stolen election conspiracy theory. Following his father's defeat, he engaged in attempts to overturn the results. He spoke at the rally that led to the storming of the Capitol, where he threatened Trump's opponents that "we're coming for you." In January 2021, Attorney General for the District of Columbia Karl Racine said that he was looking at whether to charge Trump Jr. with inciting the violent attack on the U.S. Capitol in the criminal investigation into the attack. CNN reported in April 2022 that two days after the election, Trump Jr. sent a text message to White House Chief of Staff Mark Meadows outlining paths to subvert the Electoral College process and ensure his father a second term.

At the 2024 Republican National Convention, he led the introductions of JD Vance, who had been selected as Donald Trump's running mate.

Donald John Trump Jr. was born on December 31, 1977, in Manhattan, New York City, to Ivana and Donald Trump. He has two younger siblings, Ivanka and Eric. He also has two half siblings, Tiffany, from his father's marriage to Marla Maples, and Barron, from his father's current marriage to Melania Trump. Through his father, Trump is a grandson of Fred Trump and Mary Anne MacLeod, and a great-grandson of Frederick Trump and Elizabeth Christ Trump, the latter of whom founded what became the Trump Organization. As a boy, Trump found a role model in his maternal grandfather, Miloš Zelníček, who had a home near Prague, where he spent summers camping, fishing, hunting and learning the Czech language.

His parents divorced when he was 12 years old due to his father having an extramarital affair. Trump Jr. was estranged from his father for one year after the divorce, furious at his actions which broke up the family.

Trump was educated at Buckley School and The Hill School, a college preparatory boarding school in Pottstown, Pennsylvania, followed by the University of Pennsylvania's (Penn) Wharton School, where he graduated in 2000 with a B.S. in Economics.