A man has been filmed climbing a Paris building to save a four-year-old dangling from a balcony.

Video shows the man's heroic actions as he scaled four floors in the space of just a few seconds at around 8pm on Saturday.

The man, whose identity is not known, clambered up the front of a building on rue Marx Dormoy in the 18th arrondissement of the French capital to help a child suspended in mid-air, according to Le Parisien.

Footage posted on social media shows a transfixed crowd gathered beneath the scene cheering and whooping as the man riskd his life to rescue the child.

Video of the episode has been viewed more than two million times on social media.

Firefighters were called to the incident and attended to both the child and rescuer, who were both suffering from shock.

Hero saves a 4 year old boy hanging from a balcony in Paris. What a heroic action. pic.twitter.com/TSmgqRX5Io — BNL NEWS (@BreakingNLive) May 27, 2018

The young man is said to have suffered scratches from scaling the building.

According to Le Parisien, first testimonies indicate the child was unattended and had ventured onto the balcony before getting stuck on the rail.

Independent News Service