Didier and Gabrielzinho storm to early Paralympic swimming golds
Didier, 22, was cheered on to the men's 400m freestyle S9 crown by a boisterous home crowd at the La Defense Arena.
He overtook one of the pre-race favourites, Italy's world champion Simone Barlaam, after the final turn.
Australian Brenden Hall was third, having claimed gold in the race in Rio eight years ago.
With victory for Didier, who was born with club feet and weakness in his knees, the venue witnessed similar euphoric scenes to Leon Marchand's successes during the Olympics.
Gabriel dos Santos Araujo, known as Gabrielzinho, also set the arena alight by claiming gold in the men's 100m backstroke S2.
The 22-year-old, who has no arms or hands and his legs are atrophied, celebrated his third Paralympic gold medal and making up for his silver in the event in Tokyo by blowing a puff of water from his mouth, as the crowd went wild.
Other golds went to Hungary's Zsofia Konkoly, Poland's Kamil Otowski, Singapore's Pin Xiu Yip and Denmark's Alexander Hillhouse.
Barlaam, 24, is part of a much-fancied Italian squad, who struggled in the early part of the session claiming three bronze medals on top of his silver.
Other titles are up for grabs later Thursday, including Barlaam's compatriot Franceso Bocciardo defending his 200m freestyle S5 title and another home hope in Alex Portal in the men's 100m butterfly S13.