The troubled daily said it was placing itself under the “protection of the people”, and that it was “entering a great battle for survival” just as it was most needed during an era of fake news.
A bankruptcy court hearing in a Paris suburb on Wednesday will decide its future.
With its Italian opposite number, L'Unita, folding two years ago, editors said they were determined to fight on for “workers, ordinary people, and the 'invisibles'” who keep France going.
Editor Patrick Le Hyaric said the 114-year-old publication had always supported the “thinkers who have questioned the system and the artists who have brought culture” to its highest pinnacles.
But sales slid six percent over the past year to 32,700 copies a day despite a rise in subscriptions.
Le Hyaric told AFP that he would ask the court to make sure the paper keeps publishing even if receivers are called in.
L'Humanite employs 200 people, half of them journalists.
It raised more than one million euros from readers in a few weeks last year after its future was similarly threatened.
But even that injection of cash was not enough to keep the wolves from the door, Le Hyaric said, with “no bank willing to work alongside us”.
L'Humanite's weak advertising revenues have almost dried up since 2015, the editor said, appealing for greater state support.
The newspaper was founded in 1904 by the legendary French socialist Jean Jaures, but became the official mouthpiece of the French Communist Party (PCF) after 1920.
Banned by the German occupiers during World War II, its heyday was in the 1930s when several hundred thousand copies a day were sold.
It was also an important player in the French postwar press but the decline has mirrored the fading electoral fortunes of the PCF.
In 2008 L'Humanite was forced to sell its headquarters just outside Paris designed by the Brazilian architect Oscar Niemeyer.