The 38-year-old former investment banker has barely concealed his ambition to occupy the Elysee Palace since he quit the unpopular Socialist government in August.
Macron, a business-friendly former protege of President Francois Hollande, will aim to exploit the deep divisions in the French left in his presidential run.
He has announced a press conference on Wednesday morning in a Paris suburb, with French media BFM and RTL saying he will finally put an end to speculation about his intentions.
A source in Macron's team told AFP last week that Macron would announce his candidacy in the coming weeks.
Hollande, who has the lowest popularity ratings of any post-war president, has said he will not decide until early December whether to seek re-election.
Macron has never held elected office but in April founded his own political movement, En Marche ("On the Move"), saying he wanted to promote "new ideas... neither of the right nor the left".
(Macron and his partner Brigitte Trogneux - his former school teacher. AFP)
En Marche now has more than 96,000 members and has already received 2.7 million euros ($2.9 million) in donations.
The election is currently forecast to end in a second-round runoff pitting a centre-right candidate -- likely former prime minister Alain Juppe, 71 -- against 48-year-old far-right National Front (FN) leader Marine Le Pen.
With primaries still to be contested on both left and right, Macron's chances are hard to evaluate but 38 percent of respondents to a poll published on Tuesday said he would make a good president.
They rated Juppe with 56 percent, former prime minister Francois Fillon with 38 percent -- tied with Macron -- and current Prime Minister Manuel Valls with 37 percent.
Hollande scored 17 percent, while his arch-rival, the right-wing former president Nicolas Sarkozy, had 27 percent, the same as Le Pen.
The two-round presidential election will be held on April 23 and May 7.