The migrant hero nicknamed "Spiderman" for saving a child hanging off a balcony by scaling a Paris apartment block with his bare hands has become a French citizen, according to a government decree.

Nimble 22-year-old Mamoudou Gassama from Mali was granted a fast-track to French nationality and a job in the fire service after the daring rescue in May.

"This act of great bravery exemplifies the values which help unite our national community, such as courage, selflessness, altruism and taking care of the most vulnerable," said the official document published Wednesday.

Gassama, who had been in France illegally, was catapulted to global fame by the extraordinary feat captured in footage seen by millions on social media.

The video showed the former construction worker jumping from one floor to the next, hauling himself up with impressive athleticism towards the four-year-old boy dangling above.

He was congratulated in person by President Emmanuel Macron two days later and also met Malitarget="_blank"'>