Fredriksen was born on 10 May 1944 to a welder and his wife, and grew up in Etterstad in the eastern half of Oslo.

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." Fredriksen would later become the world's 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.

Fredriksen is a widower and has two daughters: Cecilie (born 1983) and Kathrine Astrup Fredriksen (born 1983). Fredriksen's former wife, dentist Inger Astrup Fredriksen (died 2006), originally belonged to one of the Astrup families in Norway. Her Father was a professor of psychiatry, and her grand uncle was the Painter Nikolai Astrup.

In 1985, the Norwegian insurance company Gard became suspicious about losses of cargo from Fredriksen's tankers. A private investigation was initiated, and a system for the use of heavy oil as bunker fuel was revealed. The case was turned over to the Norwegian police and in June 1986 Fredriksen's offices in Oslo were searched and several of his nearest associates, and after a while also Fredriksen, were placed in detention while the case was investigated.

The Sunday Times Rich List has ranked Fredriksen's wealth as £475m (2003), £1.050b (2004) and £1.887b (2005). In 2012, Fredriksen and his family were listed as the 9th richest in Britain with a combined wealth of £6.6bn. Fredriksen owns houses in London, Oslo, Cyprus, and Marbella, Spain. He is a collector of classic Norwegian art.

In 2006, Seadrill bought more than 50 percent of Smedvig, gaining control of the company (51.24 percent of the votes and 52.27 percent of the capital). Smedvig is Fredriksen's biggest ever deal. Noble Corp sold its stake to Seadrill in 2009, leaving Seadrill with full control. Fredriksen has been the majority owner of Vålerenga I.F. for many years.

Born in Oslo, Norway, Fredriksen is a Cypriot citizen who resides in London. Before abandoning his Norwegian citizenship, he was Norway's richest man. Norwegian magazine Kapital listed Fredriksen in 2013 with a net worth of NOK 69,75 billion (US$11.9 billion). In 2012, he was included in the 50 Most Influential list of Bloomberg Markets Magazine. He was named in the top 10 most influential people in the shipping industry according to Lloyds List 2014.