About 300 jobs will be lost as global energy giant ExxonMobil closes one of the last remaining oil refineries in Australia.
The Altona plant in Melbourne has been operating since 1949 and supplies about half of Victoria's refined fuel.
But the US-based company says the operation is no longer economically viable.
"We are grateful for the tremendous efforts by our employees to improve the viability of the operation," said ExxonMobil Australia chairman Nathan Fay.
But the ExxonMobil site will be converted to an import terminal, with the refinery to continue operating for several years during the shutdown process.
Victorian Premier Daniel Andrews said the state government has been in lengthy talks with ExxonMobil, and had offered help to try and keep the plant open.
"Every effort was made to try to get a different outcome, but they've made a decision," Mr Andrews said.
United Workers Union National Secretary Tim Kennedy said the Altona workers were ExxonMobil's top-ranked employees globally.
"The closure of the Altona site, without any plan to repurpose these workers' skills for future industries, is a terrible missed opportunity," he said.
Federal Energy Minister Angus Taylor said the decision was extremely disappointing, but the closure would not impact on Australia's stockpile of refined fuel.
"The Australian government expects ExxonMobil will provide whatever support is required to assist workers and the community during this difficult time," he said.
Opposition Leader Anthony Albanese blamed the closure on the federal government.
"It is a threat to our security as a nation," he told ABC radio on Wednesday.
The growth of large-scale export refineries in Asia and the Middle East have made profits harder to come by for local refineries, and Australia's ageing plants also need ongoing capital investment.
The news of the Altona closure comes amid increasing tensions in one of Australia's major trade routes for oil, the South China Sea, and pressures on global supply chains due to the COVID-19 pandemic.
The closure means Australia will have two remaining oil refineries - the Viva Energy plant in Geelong and Ampol's Lytton facility in Brisbane.
In October last year, BP Australia announced it would cease production at the Kwinana refinery, near Fremantle in Western Australia, and convert the site to an import terminal.
Last April, the federal government moved to shore up Australia's oil reserves, establishing the nation's first government-owned fuel stockpile.
ExxonMobil plans to continue with its Gippsland Basin oil and gas joint venture with BHP, which supplies 40 per cent of the fuel needs of eastern Australia.