After being delayed by a year because of China's now-abandoned zero-Covid regime, more than 12,000 competitors from 45 nations and territories will battle it out in 40 sports.
Xi is scheduled to open proceedings in front of dignitaries including Syrian President Bashar al-Assad, who is on his first visit to ally China since the war erupted in Syria in 2011.
Leaders from Cambodia, Kuwait and Nepal will also be at Hangzhou's 80,000-capacity Olympic stadium, also known as "the Big Lotus".
Security was tight in the area around the arena, with roads closed and police stationed on street corners.
Spectators were given thorough security checks before entering and staff confiscated food and umbrellas -- at least the light rain from earlier in the day had stopped.
A military helicopter stood on a fenced-off patch of grass a few hundred metres from the stadium.
Jung-Woo Lee, sport policy expert at the University of Edinburgh, told AFP the Games were "China's post-pandemic softpower exercise".
But they have already been rocked by a row between New Delhi and China, with a trip to the city by India's sports minister cancelled on Friday.
It came after three women martial arts fighters from the Indian state of Arunachal Pradesh -- which is claimed almost in full by Beijing -- said they were denied accreditation and entry. China denied that.
In a speech ahead of the opening ceremony, Xi urged Asian nations to "use sport to promote peace, and insist on being good to our neighbours and achieving mutual benefit and win-win results".
China's status as a sporting and business destination took a severe hit during the pandemic, when snap lockdowns and strict travel rules saw almost all international events cancelled in the country.
- 'Open to all' -
The hosts are overwhelming favourites to top the medals table, with Japan and South Korea battling for second.
North Korea has sent a team, ending three years of isolation from the global sporting arena.
Games athletes will fight for medals in Olympic staples such as athletics, swimming, football, gymnastics and cycling.
ESports will make its debut as a medal event at the Games, in what is seen as a step towards inclusion one day in the Olympics.
There will also be regional specialities including dragon boat racing, the Chinese martial art wushu and kabaddi.
Nine sports, among them boxing, break dancing and tennis, will serve as Asia qualifiers for next year's Paris Olympics.
A sprinkling of world and Olympic champions adds some stardust, including India's javelin king Neeraj Chopra, Qatari high jumper Mutaz Essa Barshim and Chinese swimming royalty Qin Haiyang and Zhang Yufei.
Olympic Council of Asia honorary life vice-president Wei Jizhong said having so many sporting disciplines was about giving opportunity to as many athletes as possible.
"We are open to all. This means our Games are not concentrated only for elite sportspeople," he said.
Although the Games officially open on Saturday, sports such as football, cricket, volleyball and table tennis have already begun.
The Games will be staged at 54 venues -- 14 newly constructed -- mostly in Hangzhou but also extending to cities as far afield as Wenzhou, 300 kilometres (180 miles) south.
Hangzhou, a city of 12 million people an hour's bullet train from Shanghai, is the unofficial home of China's tech industry and the Games will feature driverless buses, robot dogs and facial recognition.
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