Fredriksen made his fortune during the Iran-Iraq wars in the 1980s when his tankers picked up oil at great risk and huge profits. As described by his biographer, "he was the lifeline to the Ayatollah."

Born on Oslo's east side, the son of a welder, Fredriksen began as a trainee in a shipbrokering company, and is now the worlds largest tanker owner, with more than seventy oil tankers, and major interests in oil rigs and fish farming. His fleet is dominated by costly double-hulled, environmentally safer tankers. He is married with 2 children, and collects classic Norwegian art, and reportedly turned down an offer of $190m (£105m) from Chelsea Football Club owner Roman Abramovich for his Chelsea home. He also has homes in Oslo, Cyprus and Marbella.

Back in December 2005 rumours circulated of Fredriksen-controlled firm SeaDrill biding for Stavanger based rig company Smedvig ASA, and since has been in a biding war with U.S. company Noble. But it was announced in late January 2006 that SeaDrill had bought more than 50 percent of Smedvig, and therefore gained control of the company (51.24 percent of the votes and 52.27 percent of the capital). Smedvig is valued at NOK 15 billion (USD 2.3 billion, GBP 1.3 billion), and is Fredriksen's biggest ever deal. SeaDrill are now expected to buy Noble's 39.5 percent of Smedvig's A-shares.

The Sunday Times Rich List 2003 (published every April) ranked Fredriksen 66th (in Britain) with a worth of £475m, in their 2004 list he ranked 30th with £1,050m, and in 2005 ranked 16th with a fortune of £1,887m. Whilst in 2005 Forbes ranked Fredriksen 160th in the world with $3,400m. And in the newly released 2006 list he has climbed to a 116th place with $5000m (the unofficial number is closer to $7 billion).

James Winchester, a veteran shipping analyst at Lazard Frères has said of him, "He's a modern-day Onassis. The tanker king. He landed squarely in the sweet spot of the tanker cycle, with the largest fleet of ships." In 2001 an article on Forbes.com described him as having "a tanker fleet bigger than anything Aristotle Onassis ever had."