The 70-year-old real estate tycoon, who took to Twitter quite early - in 2009, three years after the microblogging site was launched, has updated his bio to "President-elect of the United States".
His Twitter handle @realDonaldTrump has around 13.5 million followers, over 2 million more than President Barack Obama.
His first tweet after the election result said: "Such a beautiful and important evening! The forgotten man and woman will never be forgotten again. We will all come together as never before."
The controversial billionaire, who is also a reality TV star, has been very active on the site and threw political correctness out of the window in the presidential campaign, making personal attacks on Democratic rival Hillary Clinton, including her stamina, and invented a new hashtag of #CrookedHillary.