National Oil Companies (NOCs) are owned fully or partially by the state. Unlike the major supermajors like Exxon Mobile(XOM), BP(BP), Total(TOT), etc. the NOCs are controlled by the state though they may publicly listed as well. Some of the large oil companies in the world such as  China Petroleum & Chemical Corp (SNP) and PetroChina (PTR) of China, Petrobras (PBR) of Brazil, Equinor (EQNR) of Norway are NOCs. The map below shows the NOCs by country:

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Source: The National Oil Company Database, Resource Governance

Disclosure: Long PBR