PetroChina briefly became the world's largest company by market capitalization in 2007.
PetroChina reached the distinction on November 5, 2007, its first day of trading on the Shanghai Stock Exchange. Its shares rose sharply after the listing, briefly giving the Chinese oil producer a market value above that of ExxonMobil and other global leaders.
The company is the listed arm of China National Petroleum Corporation and is involved in oil and gas exploration, production, refining, and marketing. PetroChina had already listed shares in Hong Kong and New York before its Shanghai listing, but the mainland debut produced the dramatic short-lived valuation record.
The ranking did not last. PetroChina's share price fell substantially after the initial surge, illustrating why market-cap records based on a single trading day can be temporary. The event is often confused with PetroChina's initial public offering being the largest ever, which is a separate claim and uses different criteria.