The launch on Tuesday comes a day before a decision from Facebook Inc's oversight board on whether to uphold Trump's indefinite suspension from the platform.
Trump was barred due to concerns of further violent unrest following the deadly January 6 storming of the US Capitol by his supporters.
Trump, who left office on January 20, has falsely claimed he lost last year's election to Democrat Joe Biden because of widespread voter fraud.
The site, which was first reported by Fox News, is dubbed "From The Desk Of Donald J. Trump" and contains short posts from Trump that can be liked.
Trump's senior adviser, Jason Miller, told Fox News in March that the former president, who was banned from a slew of sites after the riot, had plans to launch his own social media site. It is not clear if this is the same platform.
Trump representatives did not immediately respond to requests for comment.
The former president has also been sending out short, emailed press releases.
Twitter Inc has said its ban on Trump is permanent, even if he runs for office again. Alphabet Inc's YouTube has said it will restore Trump's channel when it decides the risk of violence has decreased.