Khalifa Haftar, 77, said elections were the only way out of the crisis in Libya, which has suffered chaos and conflict since the uprising that, with Nato support, ousted dictator Muammar Qaddafi in 2011.
"I declare my candidacy for the presidential election, not because I am chasing power but because I want to lead our people towards glory, progress and prosperity," he said.
His announcement came two days after the candidacy of Saif Al Islam Qaddafi – the son of the fallen dictator – who has been accused of war crimes by the International Criminal Court.
Both are controversial figures.
Field Marshall Haftar announced in September that he would step down from his military role for three months in a move many saw as ensuring he qualified as a candidate in the elections that, while scheduled for December 24, are still in doubt given splits in the transitional government.
The LNA head has spent much of the past decade leading military campaigns but is now seeking power through the ballot box.
The field marshal, whose white hair contrasts with his dark moustache and eyebrows, has been a divisive but important player in Libya since the uprising.
A month after the revolt began, Field Marshal Haftar returned from two decades of exile in the US to live in the eastern Libyan city of Benghazi.
In October 2021, Qaddafi was tortured and killed by rebels.
Shortly afterwards, around 150 army officers proclaimed Field Marshal Haftar their chief of staff.
Since then, he has presented himself consistently as the man to save Libya from "terrorists and mercenaries".
In 2014, his self-styled LNA launched a blistering campaign against extremist groups in Benghazi.
After declaring victory in 2017, he moved to kick hardline groups out of Derna, the only town in the eastern region of Cyrenaica still holding out against his forces.
Those victories established him as a key player in a country now mired in a complex war between multiple militias backed by foreign players.
Field Marshal Haftar was not averse to seeking outside support himself.
With backing from Russia, Egypt and others, in 2019 he sent his forces to the country's desert south, taking the main city Sebha without a fight.
He then turned his sights on the capital Tripoli, on the western end of Libya's Mediterranean coast, vowing to "cleanse" the capital of "terrorists" backing the Government of National Accord.
Despite a rapid initial advance, Field Marshal Haftar’s forces became bogged down on the southern outskirts of the capital and were met by an intervention by Turkey that included sophisticated weapons, drones and soldiers to prop up the pro-GNA forces.
The fighting ended in a stalemate with Field Marshal Haftar pulling forces back in June 2020 and declaring a ceasefire.
The October 2020 ceasefire and a UN-backed peace process paved the way for the December elections in which Field Marshal Haftar was always expected to stand.
Announcing his candidacy on Tuesday, he said he wanted to be president "not because I am chasing power, but because I want to lead our people towards glory, progress and prosperity".
Field Marshal Haftar started his career as a Soviet-trained soldier and took part in the 1969 coup that toppled Libya's pro-Western monarchy and brought Muammar Qaddafi to power.
Once a military chief under Qaddafi, he was taken prisoner in the border area of Ouadi Doum during Libya's 1978-1987 war with Chad.
But Qaddafi disowned him, saying the general was not part of his army.
Washington managed to orchestrate his release, granting him asylum in the US, where he joined the Libyan opposition.
Now, Field Marshal Haftar’s main rival at the ballot box will be Seif Al Islam Qaddafi, who registered his candidacy on Sunday.
However, with no clear agreement on the legal basis for the election, major factions may reject the vote.
On Monday, Interim Prime Minister Abdulhamid Al Dbeibah, who may also run as presidential candidate, called for new election legislation.