A Vietnamese billionaire who came to the US as a refugee has donated $US5 million to the victims of hurricane Harvey.

The Daily Mail cited Hoang Kieu as saying the gift was his way of paying back America after being able to flee the Vietnam war and settle in the country in 1975.

The 73-year-old is the owner of a California-based company called Rare Antibody Antigen Supply which is worth $US14 billion.

According to Forbes, he has a personal worth of around $3 billion.

Hurricane Harvey became the most powerful hurricane to hit the state of Texas in more than 50 years, killing more than 60 people, displacing more than 1 million and damaging some 203,000 homes.