Australia's richest man Anthony Pratt's company is suing almost 70 workers in his packaging empire over claims of unlawful industrial action.

The billionaire businessman was named as Australia's wealthiest person in this year's Financial Review Rich List and is the chief executive of cardboard box and recycling giant Visy, which is also suing the Australian Manufacturing Workers' Union.

Mr Pratt has an estimated $12.6 billion fortune.

Visy is taking 69 workers to federal court for fines and compensation over alleged unlawful industrial action last month at a Victorian site.