A hot-air balloon brought an Olympic ring of fire into a rainy sky and singer Celine Dion performed on the Eiffel Tower as Paris kicked off its first Summer Olympics in a century with a four-hour-long, rule-breaking opening ceremony that unfurled along the Seine River.

On-and-off showers did not seem to hamper the enthusiasm of the athletes.

Some held umbrellas as they rode boats down the river in a showcase of the city's resilience as authorities investigated suspected acts of sabotage targeting France's high-speed rail network.

With the ambitious ceremony, the stakes for France were immense.

Dozens of heads of state and government were in town, and the world was watching as Paris turned itself into a giant open-air theatre.

Along the Seine, iconic monuments became stages for dancers, singers and other artists.

That included the Louvre museum, near where French judo champ Teddy Riner and three-time Olympic champion runner Marie-Jose Perec lit the Olympic cauldron, which was attached to a giant balloon that floated into the night - homage to early French pioneers of manned flight.

Despite the weather, crowds crammed the Seine's banks and bridges and watched from balconies, "oohing" and "aahing" as Olympic teams paraded in boats down the waterway that got increasingly choppy as the weather worsened.

Many of the hundreds of thousands of spectators huddled under umbrellas, plastic ponchos or jackets as the rain intensified.

Others danced and sang, and some dashed from their seats for shelter.

The weather made for some bizarre scenes at the show combining pre-recorded and live performances: a stiff upper-lipped pianist played on even as small puddles formed on his grand piano.

As global audiences tuned in, Paris put its best foot forward - quite literally, with a spectacular Olympic launch that lifted spirits and joyous French cancan dancers early on.

A humorous short film featured soccer icon Zinedine Zidane as plumes of French blue, white and red smoke followed.

Lady Gaga sang in French in a pre-recorded bit, with dancers shaking pink plumed pompoms, injecting a cabaret feel.

On the Eiffel Tower, Dion closed the show with her first live performance since the French-Canadian singer was diagnosed with stiff person syndrome, a rare neurological disorder, at the end of 2022.

More than three hours into the show, French President Emmanuel Macron declared the Games open.

In a gaffe before that, the five-ring Olympic flag was raised upside down at the Trocadero across from the Eiffel Tower.

In some memorable moments, French-Malian pop star Aya Nakamura, the most listened-to French-speaking artist in the world, emerged from a pyrotechnic display in an all-gold out to sing her hit Djadja accompanied by a Republican guard band of the French army.

The ceremony celebrated women, including 10 golden statues of female pioneers that rose from giant pedestals along the river.

Among them was Olympe de Gouges, who drafted the Declaration of the Rights of Women and the Female Citizen in 1791 during the French Revolution.

She campaigned for the abolition of slavery and was guillotined in 1793.

The Paris Games aim to be the first with equal numbers of men and women competing.

Thousands of athletes on 85 boats started the 6km parade on the Seine by breaking through curtains of water cascading down from Austerlitz Bridge.

The jetting waters were a wink at the fountains of Versailles Palace, the venue for Olympic equestrian competitions.

The Eiffel Tower, its head visible below the clouds, Notre Dame Cathedral - restored from the ashes of its 2019 fire - the Louvre Museum and other iconic monuments also starred in the opening ceremony.

Award-winning theatre director Thomas Jolly, the show's creative mind, used the signature Paris cityscape of zinc-grey rooftops as the playground for his imagination to tell the story of France, its people, their history and essence in a way designed to leave an indelible imprint on Olympic audiences.