The accord calls for a two-year power-sharing government, meant to lead Liberia into elections and out of 14 years of conflict brought on by Taylor.
The two rebel movements — Liberians United for Reconciliation and Democracy, and the Movement for Democracy in Liberia — signed, along with representatives of Liberia's post-Taylor government.
Under the deal, all three waive any claim on the top posts in the interim government — yielding control to non-combatants.
"I want to believe that with the signing of this agreement today, Liberia will never be plunged into another spiral of violence in the quest for political power, or under the false pretense of liberating the people," said retired Nigerian Gen. Abdulsalami Abubakar, chief mediator for the talks.
"Liberians do not need liberators anymore. Liberians need developers and nation-builders," Abubakar said.
Ghana President John Kufuor was on hand for the agreement, and representatives of the United Nations, European Union and African Union signed as witnesses.
The United States has had an influential delegation at the talks, and signed as witnesses to a June 17 cease-fire accord — but it says West Africa must take the lead in Liberia.
News of the peace accord came after dark in Monrovia, where hundreds of thousands still stay indoors for fear of gunmen, and few have batteries or electricity for radios after 10 weeks of rebel siege.
The deal comes a week after the resignation of Taylor, who flew into exile at the demand of rebels, West African leaders and the United States.
Taylor launched once-prosperous Liberia into conflict in 1989, leading a small insurgency. The seven-year civil war that followed killed at least 150,000 and ruined virtually every city and town in the country.
Taylor won the presidency in 1997, elected largely out of fear he would reignite fighting if he lost. The northern-based Liberians United group launched their insurgency in 1999, and were joined late last year by the Movement for Democracy in Liberia, based on the Ivory Coast border.
Liberia's combatants have broken all past peace accords and returned to fighting.
Liberians and the international community have held out hope that Taylor's departure, and a promised U.N. peace force, will make a difference this time.
"Any agreement that sticks is to the benefit of the humanitarian situation, and the people of Liberia," Ross Mountain, the top U.N. humanitarian official in Liberia, said Monday.