Haftar later officially submitted his bid at an electoral board office, where he told journalists: "The next stage will be difficult. I call on all Libyans to make the right choice, one they will not regret."
His candidacy marks the latest stage in Haftar's dramatic trajectory from exile in the United States to becoming one of the most controversial figures in Libya's 10-year conflict.
From 2014, he led a three-year battle against jihadists in Benghazi, establishing himself as the dominant power in the country's east.
In April 2019, backed by Russia, Egypt and the United Arab Emirates, he launched an offensive on Tripoli on the pretext of rooting out militant groups.
The year-long battle left the outskirts of the capital in ruins and Libya more divided than ever. But a United Nations-brokered ceasefire in October last year paved the way for a peace process leading to elections set for 24 December.
In September, Haftar provisionally quit his military position in line with a controversial electoral law to allow him to run for president.
On Tuesday, wearing a formal suit and tie instead of his military uniform, he said the vote is "the only way to pull Libya out of chaos".
Libya's electoral process, already beset by disputes over who can stand and the legal basis for the polls, looks as shaky as ever just six weeks ahead of the vote.
On Monday evening, the head of the UN-backed unity government Abdulhamid Dbeibah said the process was facing "huge" problems given the lack of laws and consensus over a constitutional framework for the vote.
Last week, Haftar's forces said 300 mercenaries fighting on his side would leave Libya at the request of France in a "unilateral gesture", expecting nothing in return from the government in Tripoli.
But pro-Haftar forces remain in control of much of eastern and southern Libya, and some analysts have voiced scepticism over the chances of a free and fair vote.
Analyst Khaled al-Montasir said Haftar had "imposed himself on the political scene, but he will remain a controversial figure rejected by many in western and southern Libya".
"Moreover, there's no guarantee that any election process that brings him to power will be respected," he told AFP.
Other analysts warned of the potential for intimidation or worse from Haftar loyalists.
"Haftar's forces have by far been Libya's leading perpetrators of war crimes since 2014, and are bound to use intimidation or worse to influence the elections," tweeted Wolfram Lacher, a Libya specialist at the German Institute for International and Security Affairs.
Next month's election is seen by the international community as a key step in restoring stability to Libya after a decade of conflict since the overthrow of Kadhafi in a NATO-backed uprising.
But the path to the ballot box has been lined with disputes over the constitutional basis for the polls and the powers to be given to whoever wins.
Many observers have warned there are no guarantees either side will respect the result of the election.
"Haftar claimed in 2018 Libya was 'not ripe for democracy', and last August that his military forces would not be subject to any political authority, civilian or otherwise," Anas El Gomati, director of Libya-based think tank the Sadeq Institute, told AFP.
"This is a major threat to the political transition moving forward."