Nuaman Gumaa, leader of the New Wafd Party, becomes only the second major challenger so far to 77-year-old President Hosni Mubarak, who has ruled Egypt since 1981.
Mubarak, a former air force fighter pilot, announced his candidacy last week and is widely expected to win a fifth term in the 7 September balloting, despite having opened the field to challengers for the first time.
Previously, presidential elections have been referendums in which voters said yes or no to one candidate selected by parliament.
"We are critical of a lot of things, but it doesn't mean we don't participate in the political process," said Munir Fakir Abd al-Nur, a prominent lawmaker who pushed New Wafd to take part in the vote.
He predicted Gumaa would take 20% of the vote.
Opposition groups, including the New Wafd, claim election laws virtually ensure Mubarak's re-election, although Gumaa's candidacy could help Mubarak blunt criticism that he had no viable opponent.
The other major challenger is Ayman Nur, a former New Wafd member who founded his Al-Ghad or Tomorrow Party last year.
Nur is standing trial for forging papers to register his party, but has pledged to compete in the elections.
Five minor parties with no members of parliament have registered candidates, but they are little known.
The New Wafd party grew out of Egypt's oldest liberal party, the Wafd, or Delegation, founded in 1919.
It was outlawed in 1953, after President Gamal Abdel Nasser took power in a military coup, abolishing political parties.
It re-emerged in 1978 when political parties were re-instituted, only to be disbanded the same year. The current New Wafd Party was formed in 1983.