A ceasefire agreement has long been considered one of the last and most important steps to help end Colombia's 52-year armed conflict.
Peace talks started in Havana in November 2012
, but both parties have yet to negotiate a number of issues before signing a final agreement.
President Juan Manuel Santos called the occasion a "historic day" for his country, which has lived for five decades "with the fear and uncertainty of war."
"After more than 50 years of clashes, deaths, attacks, death and sorrow, we have put an end to the armed conflict with the FARC. Reaching this agreement fills us with faith and hope," Santos said afterward.
Santos, a former defense minister who fiercely fought the FARC during his tenure from 2006 to 2009, shook hands with Rodrigo Londoño Echeverri, the top FARC leader better known as Timoleón "Timochenko" Jiménez, his nom de guerre.
"Let this be the last day of war," Londoño told an audience of regional leaders, including the presidents of Chile, Venezuela, the Dominican Republic, El Salvador and Mexico.
U.N. Secretary-General Ban Ki-moon also attended the signing ceremony as well as representatives from Norway and the United States.
Londoño addressed critics, who say the FARC wants to have its cake and eat it, too, meaning, the rebels want to be a political party but still refuse to lay down their weapons.
"The country will be able to see it starting today," Londoño said. "Of course, we will get into politics! That's our reason to exist. But we will do it using legal and peaceful means with the same rights and guarantees that other (political) parties enjoy," he said.
Cuban President Raul Castro, who has acted as mediator since the peace talks began nearly four years ago, said, "There will be no turning back for the peace process."
While a groundbreaking deal between the Colombian government and the FARC, the agreement does not include other guerrilla and paramilitary groups.
Santos said earlier this week that he expected the final peace deal to be reached by July 20. A referendum then would be called for Colombians to vote on whether to accept or reject the agreement.
The Colombian civil war has been one of the longest armed conflicts in the world. In 1964, the FARC, the Spanish acronym for Revolutionary Armed Forces of Colombia
, formed as a peasant, rebel army to repel military attacks.
The FARC sought to emulate the Cuban revolution and install a Marxist-style government in the South American country.
In later decades, it became a violent guerrilla movement, perpetrating terrorist attacks, kidnapping high-profile government officials and getting into drug trafficking.
Billions of dollars in U.S. counterinsurgency aid has helped the Colombian government turn the tide against the FARC, which suffered as top commanders were killed and thousands of foot soldiers abandoned the insurgency.
The war between the FARC and Colombian government has left an estimated 220,000 dead. About 5 million people have been displaced, according to some estimates.