Emergency services are on the scene at the steelworks in Port Talbot.
Tata Steel UK has confirmed the news on Facebook and Twitter.
Councillor Rob Jones, leader of Neath Port Talbot Council, said: "I was deeply saddened to hear the tragic news from Tata Steel this afternoon.
"I would like to offer my deepest sympathy to the family of the deceased and to his friends and colleagues. Port Talbot has strong links with Tata Steel and the workers at the plant, and I know that our local communities will be feeling a mixture of shock and sadness at this time.
"Tata has launched a full investigation into the incident and we stand ready to offer whatever support is required."
The Welsh Conservative Shadow Minister for Economy and Transport, Russell George AM said: “My thoughts go to the family and friends of the person who has died today, and to the close knit Tata Steel community in Port Talbot and across Wales.
“Heavy industry is a major part of the Welsh economy and we must make sure that these industries keep their employees safe whilst at work.”
Suzy Davies AM, Regional Assembly Member for South Wales West added: “Details are still sketchy but the news that someone has lost their life at Port Talbot steelworks today is very saddening.
“I’m sure that the incident will be fully investigated and we will know more in due course, but for now our thoughts are very much with the family and friends of this poor individual.”