The Republican nominee's projected victory came down to a handful of key swing states, despite months of polling that favoured Mrs Clinton.
The battlegrounds of Florida, Ohio and North Carolina cleared the way for his Brexit-style upset.
Global markets plummeted, with the Dow set to open 800 points down.
Mr Trump's projected victory in Wisconsin put him over the 270 out of 538 electoral college votes needed to win the White House.
The US president-elect took to the stage at his victory rally in New York and said: "I just received a call from Secretary Clinton. She congratulated us on our victory."
"It is time for us to come together as one united people."