document: 16 January 2017 Last updated at 12:32 GMT
  The ceremony is called the inauguration.
  At the event, he will make a promise to do the best for the country and will give a speech known as the inaugural address.
  There are a few traditions passed down, which he must observe on his inauguration day.
  Leah takes a look at what's going to happen throughout the day...
summary: On Friday, Donald Trump will officially become the next president of the United States.