The enormous femur was dug up in a fossil-rich area in Charente, and dates back 140million years.
Sauropods are the largest herbivorous dinosaurs known to date – and include diplodocus, brachiosaurus and brontosaurus.
They first appeared in the late Triassic Period, but this particular dino is from the Jurassic era.
It was discovered “nestled” in a thick layer of clay by volunteers from the National Museum of Natural History.
The bone itself weighs an incredible 500kg – just heavier than an average modern horse.
Sauropods were some of the biggest creatures ever to walk the EarthCredit: Getty – Contributor
And it was discovered alongside a giant pelvis bone hidden within the same layer of clay.
Charente is best known for the town of Cognac – home to the brandy – but it’s also a hotbed for fossils.
Palaeontologists have already uncovered around 7,500 bones from the site since 2010.
It’s estimated that these bones are linked to as many as 45 different species of dinosaurs.
But the femur is the biggest bone uncovered from the site so far.
“This femur is huge! And in an exceptional state of conservation,” said Jean-François Tournepiche, Angouleme Museum curator, speaking to The Local.
“It’s very moving,” he added.
Experts believe that the femur likely belonged to a sauropod, which is one biggest dinosaurs ever to roam Earth.
The world-famous class of dinos are identified by their long necks and plant-based diets.
And the bone itself still provides important details that only a trained eye would spot.
“We can see the insertions of muscles and tendons, scars,” explained Ronan Allain, a palaeontologist at Paris’ National Museum of Natural History.
“This is a very rare find as large pieces tend to collapse on themselves, to fragment.”