He also pleaded for an extension of a significant grain export deal due to expire soon.
Mr Zelensky appeared in a video speech beamed to leaders gathered on the Indonesian island.
Vladimir Putin, the leader of Russia - a member of G20 - refused to attend and sent his foreign minister Sergei Lavrov instead.
In his speech, first reported by AFP, Mr Zelensky said: "I am convinced now is the time when the Russian destructive war must and can be stopped."
He outlined a number of strategies, including ensuring nuclear and food safety, the ending of hostilities, and a prevention of escalation.
He repeatedly addressed the leaders as the "G19" - pointedly excluding Russia.
Chief among his requests was an extension of what is known as the Black Sea grain deal which was struck in July between the United Nations and Russia.
It has ensured that food exports blocked at Ukrainian ports by Russian warships can be shipped out.
The UN says since the deal began, 10 million tonnes of grain and other food have been successfully exported, helping to stave off a global food crisis.
But the deal expires on 19 November. Speaking on Tuesday at a G20 session on food security, Mr Zelensky said the deal should be extended indefinitely, "no matter when the war ends".
"The right to food is a fundamental right of every person in the world," he said, proposing to expand the deal to other ports in the Mykolaiv region.