Mr Trump, who has previously toyed with running for the presidency, told a crowd of supporters at his Trump Tower skyscraper in Manhatten that he will be “the greatest jobs president that God ever created”.
He added: “We need somebody that can take the brand of the United States and make it great again. We need somebody that literally will take this country and make it great again. We can do that.”
The outspoken TV celebrity joins an unusually large field of Republicans vying for the presidential nominations.
Mr Trump will be widely seen as having little chance of securing the Republican nomination, but his addition to the race will no doubt enliven proceedings.
The host of NBC’s “Celebrity Apprentice” famously questioned the authenticity of Barack Obama’s birth certificate, leading to mocking from the US president in the 2001 White House correspondents’ dinner (see video below).
Mr Trump has previously said that he is “pro-life” and “against gun control”. He will be competing against a host of Republican big hitters, including Jeb Bush, who launched his campaign on Monday.
Other favourites for the nominations include Wisconsin governor Scott Walker and Texas senator Ted Cruz.