UN monitors "today have the entirety of the FARC's registered individual arms stored away," except for some that were exempted for transitional security at demobilization camps, the body said in a statement.
The disarmament by the roughly 7,000 members of Colombia's biggest rebel group under a 2016 peace accord brings Latin America's oldest civil conflict close to a complete end.
But the process has been blighted by ongoing violence involving other groups.
FARC leader Rodrigo Londono, also known by his nom de guerre Timochenko, is scheduled to formally conclude the disarmament process at a ceremony with President Juan Manuel Santos in the central town of Mesetas at 1500 GMT on Tuesday.
7,000 weapons
The UN statement said the FARC had handed over all of its more than 7,000 weapons, excluding "those that under the roadmap will be used for security in the 26 camps" until August 1.
Separately, the UN mission is continuing to extract and destroy other weapons and munitions stashed in remote hiding places which the FARC have identified and surrendered to the monitors.
Londono called the disarmament "a historic moment for Colombia," ahead of Monday's UN announcement.
"The laying down of arms is an act of will, courage and hope," he wrote on Twitter.
Santos said last week that the event "changes the history of Colombia."
"The FARC, the most powerful and oldest guerrilla force in Latin America, will cease to exist," he said in a speech in Paris.
FARC's future
The former fighters are now due to make the transition into civilian life. The Revolutionary Armed Forces of Colombia (FARC) will transform into a political party.
Weapons "fulfilled a function at one time, but today we are making a political decision and we no longer need them," senior FARC commander Mauricio Jaramillo told AFP.
The accord, first signed in November, was initially narrowly rejected by Colombians in a referendum before being redrafted and pushed through congress.
Critics such as conservative political leader Alvaro Uribe said it was too lenient on FARC members, some of whom will get amnesties or reduced sentences for crimes committed during the conflict.
Ongoing violence
Colombia's civil conflict erupted in 1964 over land rights. It drew in leftist guerrillas, right-wing paramilitary groups and state forces.
It has left 260,000 people confirmed dead, more than 60,000 missing and seven million displaced.
Santos says he wants to seal a "complete peace" by reaching a deal with the country's last active rebel group, the leftist National Liberation Army (ELN).
The ELN started talks with the government this year, though it has been blamed for ongoing confrontations with state forces.
It kidnapped two Dutch journalists on June 19 and freed them five days later.
Officials say remnants of right-wing paramilitary groups are also fighting the ELN in rural areas for control of the drug trade that has fueled the conflict.
Three women were killed in a bombing at a crowded shopping center in Bogota on June 17. That was blamed on a fringe extremist group, the Revolutionary People's Movement (MRP).
Eyewitness? Submit your stories now via social or:
Email: news@pulselive.co.ke
