CNOOC Limited (中国海洋石油有限公司) is China’s largest producer of offshore crude oil and natural gas. It is a major subsidiary of China National Offshore Oil Corporation (CNOOC) and has been listed in Hong Kong SEHK: 0883 and in New York NYSE: CEO since February 2001. It was admitted as a constituent stock of the Hang Seng Index in July 2001. In September 2013 it was listed on the Toronto Stock Exchange following its acquisition of Canadian oil and gas company Nexen Inc.

Its core domestic operation areas are in Bohai, the South China Sea, and the East China Sea. Internationally, it has oil and gas assets in Asia, Africa, North America, South America, and Oceania.

As of December 31, 2011, the CNOOC Limited owned net proven reserves of approximately 3.19 billion barrel of oil equivalent (BOE), and its average daily net production was 909,000 BOE.

CNOOC Ltd's parent, China National Offshore Oil Corporation (CNOOC), is the third largest of the "Big Three" Chinese oil companies, and traditionally specialised in offshore upstream exploration and production, whereas CNPC Group specialised in onshore upstream exploration and production, and Sinopec Group specialised in refining and marketing. These distinctions are now increasingly blurred as the three companies compete in all areas. All of the "Big Three" have vested the majority of revenue producing assets in listed Hong Kong subsidiaries. CNPC into PetroChina, Sinopec Group into Sinopec Limited, and CNOOC Group into CNOOC Limited.