"I am running for president to finally put the issues concerning most Americans on to the front burner," the 48-year-old civil rights activist said in a statement.
He expects to file papers with the Federal Elections Committee on Jan. 21, spokeswoman Rachel Noerdlinger said.
"I'm qualified, probably more qualified than any other person who is expected to be on the Democratic ticket for 2004, because I actually have a following and I speak for the people," said Sharpton, who has never held public office.
Preparing for the campaign, Sharpton criss-crossed the country last year giving speeches and wrote a book titled "Al on America" that was released in October. In the book, the black leader said presidential politics has become "an exclusive club for white males, of a certain income, of a certain age."
Sharpton unsuccessfully sought the Democratic nomination for Senate in 1994 and the party's mayoral nomination in 1997.
As head of the civil rights group National Action Network, Sharpton has been considered a polarizing figure by many. But he has moderated his positions in recent years, aligning himself more closely with the party establishment.