The contractor, believed to be aged in his 20s, died at the Port Kembla steelworks after an incident on Monday morning as he worked opposite the No.5 blast furnace stockhouse.
BlueScope said its preliminary understanding indicated a steel beam being lifted by a crane fell and fatally struck the man.
Paramedics and police were called but the worker died at the scene.
"Our immediate priority is supporting our people, the first responders and the family of those involved," a BlueScope spokesman said.
"We are deeply saddened by this tragedy."
Police have initiated an investigation, SafeWork NSW has been notified and a report will be prepared for the coroner.
The steelworks, south of Wollongong, is the largest manufacturer and supplier of flat steel in Australia.
Its history traces back to the Hoskins family relocating their steel business from Lithgow to Port Kembla in the late 1920s, with the plant growing to 760 hectares in size.
BlueScope announced in 2023 it would spend $1.15 billion in an attempt to lower emissions and extend the life of the steelworks.
Work to reline the dormant No.6 blast furnace got underway in 2024 as the No.5 blast furnace approached the end of its life span between 2026 to 2030.
The reline was expected to be completed by mid-2026.
In August, BlueScope chief executive Mark Vassella said decarbonising the steelworks would cut the company's carbon emissions by 60 per cent.
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