Speaking at an Australian Strategic Policy Institute event on Tuesday, Vasyl Myroshnychenko said there was still a great deal Australia could do to assist Ukraine following Russia's invasion two months ago.
Mr Myroshnychenko warned of dire global consequences if military assistance such as weapons was not supplied.
"We need it all to be able to defend, to defend Ukraine, defend Europe, and defend all the values and freedom and democracy," he said.
"We are there in the trenches for you people, because ... the consequences we're going to see will be enormous, that (Vladimir Putin) can take another country by force.
"This is going to create a domino effect all over the world, including here in the Indo-Pacific."
Ukraine's ambassador said he was buoyed by Australia's swift support in imposing sanctions against Russia and supplying military equipment such as several Bushmaster vehicles.
Mr Myroshnychenko said Australia would play a crucial role in the reconstruction of Ukraine once hostilities cease.
"We need to rebuild roads, infrastructure products, ports, this is where we'll need your support," he said.
"And I'm sure Australia could do a great deal."
The comments come as Russia's foreign minister told the world not to underestimate the risks of nuclear conflict.
Sergei Lavrov said NATO's supply of weapons in Ukraine meant the Western alliance was engaged in a proxy war in Russia.
Meanwhile, Sweden and Finland have agreed to submit an application to join NATO following Russia's invasion.
It's reported the two nations could submit the application as early as next month.
Mr Myroshnychenko said it was encouraging that more countries were looking to join NATO and support Ukraine following the conflict.
"It's reassuring to see the support coming from Finland and Sweden," he said.
"The popularity of these countries joining NATO was still not enough three months ago."
The ambassador said Russia's invasion of Ukraine had also led to the collapse of pro-Russian sentiment in large parts of the Ukrainian community.
"Whatever pro-Russian sentiment which existed in Ukraine, it evaporated as a result of this invasion," he said.
With the conflict still ongoing in many parts of the country, Mr Myroshnychenko warned President Putin was still trying to establish a "new world order", in an attempt to revive the Soviet Union.
"We're protecting our own country, we're protecting our own sovereignty," he said.
"It's an existential war for us, it's a matter of survival to defend, because the plan that Russia has announced is the plan to take over the country and totally subjugate the country."
