Ayman Nur's statement of intent on Wednesday makes him the first person to challenge the governing National Democratic Party (NDP) in nearly 24 years of rule by President Husni Mubarak.
Nur made the announcement at the doorstep of the charity he runs in his constituency in Islamic Cairo. He addressed a crowd of more than 1000 people in the street.
The building was surrounded by a heavy contingent of riot police who tussled with the crowd before Nur's arrival.
"With thanks to God, the party, to you and to your love, I announce here that we are going to participate in the upcoming election for the presidency of the republic against the National Democratic Party. And this party will fall," Nur said.
"They have to apologise for the false elections during the past miserable 50 years. We have never chosen a president before... Change is coming one day, and that day is soon."
"They have to apologise for the false elections during the past miserable 50 years. We have never chosen a president before... Change is coming one day, and that day is soon"
Egyptian presidential candidate
The crowd responded with chants of "Allahu Akbar (God is great)".
Earlier, when Nur arrived at the building, his supporters shouted: "Welcome, Mr President", and threw candies as he blew kisses.
The populist, pro-reform Nur, whose al-Ghad party has seven legislators in the 454-seat parliament, was freed from prison last Saturday after spending six weeks in detention on suspicion of forging nearly 2000 signatures to obtain a license for his party last year.
He denies the charge, saying his arrest was an attempt to eliminate him as a rival to Mubarak.
Nur's detention gained international attention, largely because he has championed the call for multi-candidate presidential elections.
Strong US concerns
US Secretary of State Condoleezza Rice said she raised "very strong concerns" about the detention when she met Egypt's foreign minister in Washington last month.
His intended candidacy comes after Mubarak made a surprise announcement on 26 February asking parliament to amend the constitution to allow multi-candidate elections for the first time when Egyptians go to the polls in September.
President Husni Mubarak has
ruled Egypt for 24 years
Egypt traditionally holds plebiscites in which voters say yes or no to a single candidate who has been approved by parliament, which has been dominated by the ruling party since the 1970s.
Mubarak has won four such referendums, each time with a yes vote of more than 90%.
The president has hinted he will stand again, although it is widely expected that if the 76-year-old decides not to run the ruling NDP will nominate his son, Gamal.