Oslo - Helge Lund, the chief executive of Norwegian energy group Statoil for the past 10 years, left the firm with immediate effect on Wednesday, the state-controlled company said.
Lund became Statoil chief executive in August 2004.
During his tenure, Statoil's daily production of oil and gas increased from about 1.1 million to 1.9 million barrels of oil equivalent.
Lund also oversaw Statoil's merger with Norwegian group Norsk Hydro's oil and gas division.
The Statoil board said Eldar Saetre has been named acting chief executive.
Lund is set to join British-based energy group BG Group in March, BG Group said.
“I could have continued for a period, but there is a time for everything. Renewal is important, both for Statoil and for me. I came to the conclusion that the time was right for a change,” Lund said in a statement issued by Statoil.
Sapa-dpa