Leaders from the world's 20 largest economies have descended on the resort island of Bali for annual talks.
But as usual, many significant and intriguing events are occurring on the sidelines of the summit.
After much speculation, China's President Xi Jinping and Australia's Prime Minister Anthony Albanese sat down for formal talks.
The meeting was relatively short and didn't produce any concrete agreements, but the fact it happened at all is a significant moment in China and Australia's relationship.
The war in Ukraine has also been a major G20 talking point.
But confusion over a rumoured hospital trip seemed like it might derail Russia's presence at the gathering.
Here are the biggest moments from the first day.
Xi and Albanese meet face to face — but only for 32 minutes
It was a relatively short meeting — just half an hour compared to the three hours Mr Xi set aside to talk to US President Joe Biden on Monday.
But it's the first time an Australian prime minister has sat down with China's leader for major talks since 2016.
In a press conference afterwards, Mr Albanese implied there was no need to read anything into the duration of the meeting.
"It went overtime, when it was scheduled," he said.
"It was a warm discussion."
Australia and China have many complex issues to sort out, including trade disputes, the origins of the COVID-19 pandemic and Beijing's growing presence in the Pacific.
Mr Albanese said he did not expect resolutions to be found in one short conversation, but both countries have taken an important step to "moving forward".
"There are many steps, of course, that we are yet to take," he says.
"I have said consistently since before I became prime minister, we will cooperate where we can, [and] disagree where we must act in the national interest."
The significance of meeting 'halfway'
Anthony Albanese had been managing expectations for his meeting with the Chinese president, suggesting the mere fact they are meeting is a success.
That's before we even talk about whether Australia is out of Beijing's diplomatic deep freeze.
Chinese state media described the talks as an opportunity for the two countries to meet "halfway".
It's a fairly innocuous description, but when you think about it, it's actually pretty loaded.
Australia and China both have issues they won't budge on, so movement to a halfway position is highly unlikely.
World leaders are lining up to meet Xi Jinping, for a number of reasons.
Firstly, it's been a while. He's been pretty wary of travelling since the COVID-19 pandemic hit.
Secondly, Mr Xi is a powerful player on the world stage.
Not only is he a big deal in the Asia Pacific region, but he has considerable sway over affairs further afield, such as Russia's invasion of Ukraine.
Xi Jinping remains one of the only world leaders who has maintained a relationship with President Vladimir Putin even after he invaded Ukraine earlier this year.
The Russian leader opted to skip this year's summit, but he did send Foreign Minister Sergey Lavrov to Bali.
Russia's diplomat denies hospital reports
Mr Lavrov's arrival in Bali last night was surrounded by drama, confusion and rumour.
Soon after his plane arrived, the Associated Press reported that he'd been taken to a hospital, with some sources claiming he had a "heart condition".
Bali's Governor Wayan Koster said the Russian diplomat went to Sanglah Hospital "for a health checkup", but was well enough to be discharged.
The ABC was also told by the hospital that two Indonesian secret service agents had been there.
But a spokeswoman for Mr Lavrov hit back at the reports, calling them the "highest level of fakery".
She also posted a video of the diplomat on social media platform Telegram, in which he appeared to be relaxing outside his hotel room in shorts.
"They've been writing about our president (Vladimir Putin) for 10 years that he's fallen ill. It's a game that is not new in politics," Lavrov said in the video.
Soon after the G20 began, Ukraine's President Volodymyr Zelenskyy gave a passionate speech via video link in his signature khaki t-shirt.
He told leaders that Russia must not be allowed to rebuild its forces and wage a new campaign of terror in the wake of its withdrawal from Kherson.
"I am convinced now is the time when the Russian destructive war must and can be stopped," he said.
Kyiv also welcomed Chinese comments criticising threats to use nuclear weapons, after the Biden-Xi meeting on Monday.
The two leaders "underscored their opposition to the use or threat of use of nuclear weapons in Ukraine," the White House said in a readout of their encounter.
The US expects the G20 leaders to condemn Russia's war in Ukraine and its impact on the global economy, a senior US official said.
Joko Widodo issues a stern warning to the world
The summit host, Indonesian President Joko Widodo, used his opening speech to issue a stark warning about the "incredible challenges" the world is currently facing.
He identified the ongoing COVID-19 pandemic, rivalry and war as well as its impact on food security, energy and finances as crises that are being felt globally, "especially by developing countries".
"If the war does not end, it will be difficult for the world to move forward. If the war does not end, it will be difficult for us to take responsibility for the future," he told the summit.
"We have no other option, collaboration is needed to save the world."
Mr Widodo called for unity and concrete action to mend the global economy despite deep rifts over the war in Ukraine.
"G20 must be the catalyst for inclusive economic recovery. We should not divide the world into parts. We must not allow the world to fall into another cold war," he said.
The Indonesian leader also warned of a worsening global food shortage — with developing nations facing the highest risk — if war is allowed to continue.
