After Amsterdam and Cologne, Paris became the third European city to host the Gay Games, this year marking the 10th such event.
Some 10,000 participants, both heterosexual and LGBT, are expected at the quadri-annual sports event.
More than 90 countries are represented, including nations like Uganda, where homosexuality is illegal.
"I am very happy to be here," Jai, a transgender participant from Uganda, told France Info website. "Most homosexual competitors in my country cannot freely practise their sport."
Rainbow runs, discotheques and prizes for all
The Gay Games kick off with the International Memorial Rainbow Run, a race commemorating victims of Aids and breast cancer.
The opening ceremony features a parade with the 10,000 participants, followed by a show themed on coming out of the closet.
The event continues late into the night at the Grand Palais museum, which has been converted to a discotheque for the ceremony.
The competition is probably the first of its kind with a unique twist - there are no prizes for the winners.
Instead, everybody who participates receives a medal.
Pascale Reinteau, the competition's copresident says it's because the Games wish to "promote self-emancipation rather than a win-at-all-costs attitude".
The Gay Games closes on 11 August with a special event at the Paris Docks.
More than 35 categories of sporting events have been announced in and around Paris, with windsurfing competitions being held in the city of Le Havre.
Created in 1992 in San Francisco, the Gay Games aim to change stereotypes and fight against LGBT prejudice.