If Mr. Trump wins in November, 39-year-old JD Vance, a former venture investor, will take over as vice president.
Using his social media account, Truth Social, the former president made the announcement.
Mr. Vance, a New York Times best-selling author from Ohio, joined the venture capital industry following his Yale Law School graduation.
The former US Marines became well-known in 2016 after publishing his autobiography Hillbilly Elegy: A Memoir of a Family and Culture in Crisis, which described his Ohioan background and socioeconomic struggles.
Mr. Vance previously referred to himself as a “never Trumper” and sharply criticized the president following his election victory in 2016.
