The Philippines has signed a framework peace plan with the country's largest Muslim rebel group, the Moro Islamic Liberation Front (MILF).
The deal follows lengthy negotiations aimed at ending a 40-year conflict that has cost an estimated 120,000 lives.
The agreement was reached in early October after talks in Malaysia.
It provides for a new autonomous region in part of the south where Muslims are a majority in a mainly Catholic nation.
The framework deal was signed by the chief negotiators of the government and the rebels, and witnessed by President Benigno Aquino and MILF leader Murad Ebrahim at the presidential palace in Manila.
The two leaders met and exchanged gifts ahead of the signing. Murad Ebrahim, said to be in his 60s, is the first MILF leader to visit the palace.
''This is the sound of peace,'' he said, banging on a traditional Muslim gong that he presented to Mr Aquino.
Malaysian Prime Minister Najib Razak, who had helped to broker the deal, was also present.
"We are men and leaders who want to make a difference and we have decided that the time has come for us to choose the moral high ground," he said. "After four decades, peace is within reach."
'Devil in details'
Mr Aquino, who announced the deal a week ago, has warned that there are challenges ahead.
"As the saying goes, the devil is in the details. Much work remains to be done in order to fully reap the fruits of this framework agreement," he said just before the deal was signed.
Previous peace efforts have broken down and negotiations with the MILF over the last 15 years have been interrupted by violence.
A copy of the framework deal says the parties are to commit to reaching a "comprehensive deal" by the end of the year.
It is hoped that the agreement could be implemented on the ground by the end of Mr Aquino's term in 2016.
Both sides in this deal know it is only the beginning - the agreement is just a framework and many more details need to be added, says the BBC's Kate McGeown in the Philippines.
But for now, Filipinos are cautiously optimistic that they are one step closer to peace, our correspondent adds.
Muslims held a vigil in Manila over the weekend to show support for the agreement.
The new autonomous region would be named Bangsamoro, after the Moros - or Moors, which was how the Spanish used to refer to the followers of Islam - living there.
The draft agreement would give the leaders of Bangsamoro more political and economic powers, and provides for the gradual transfer of law enforcement from the army to the Bangsamoro police in a "phased and gradual manner".
The framework also promises the people a "just and equitable share" of the region's abundant natural resources, and pledges to address the needs of poverty-stricken communities.
The MILF, created after a split with another rebel group in 1977, had earlier dropped its demand for an independent Muslim state.
The Philippines has faced separatist movements for decades in Mindanao, where the MILF is based, and in Jolo, home to the radical Islamist Abu Sayyaf group, which is reputedly linked to al-Qaeda.
Communist rebels have also waged a guerrilla conflict over parts of the country from 1969.