"The leadership of the Ulster Volunteer Force and Red Hand Commando today confirms it has completed the process of rendering ordnance totally and irreversibly beyond use," the UVF and the RHC said on Saturday.
The statement was read to reporters in Belfast, the province's capital, by a man representing the groups and wearing an ordinary suit, a change from the past when paramilitary spokesmen would address the media in masks, toting guns.
The UVF and RHC's decommissioning exercise, carried out in co-operation with the Independent International Commission on Decommissioning, was verified by the British and Irish governments,
"The leadership of the UVF and RHC have delivered on what they said they would do," Shaun Woodward, Britain's secretary of state for Northern Ireland, said.
Micheal Martin, Ireland's foreign minister, said: "In recent years loyalist organisations have been making effective progress towards conflict transformation, and today is an important landmark in this process."
Northern Ireland has enjoyed relative peace since a 1998 deal ended the predominantly Catholic IRA's 30-year military campaign to end British control of the province and unite the island of Ireland.
The Ulster Defence Association, which together with its allies the Ulster Freedom Fighters (UFF) had fought against the IRA since the early 1970s, said it had also embarked on a process towards full decommissioning.
"The struggle has ended," the UDA said in a statement. "Peace and democracy have been secured and the need for armed resistance has gone. Consequently we are putting our arsenal of weaponry permanently beyond use."
Efforts to consolidate peace were challenged in March when Republican splinter groups - the Real IRA and the Continuity IRA - killed two British soldiers and a policeman.
But strong condemnation of the attacks from all sides of the political spectrum and on both sides of the border ended up uniting much of the province's population in favour of expediting the peace process.