Saudi Aramco's stock rose sharply as the world's biggest share sale got underway in Riyadh, rising 10% above the initial public offering price.
Last week the oil giant, which produces more than a tenth of global crude supply, raised $25.6bn (£19.5bn).
Saudi Arabia's royal family is privatising assets as part of a plan to move the kingdom away from its reliance on oil.
The money raised from the sales will be used for non-energy investments.
The record-breaking initial public offering (IPO) gave Aramco a market valuation of $1.7tn, making it the world's most valuable public company.
That was less than the $2tn targeted by Crown Prince Mohammed bin Salman.
But it is still the biggest share sale to date, surpassing that of China's Alibaba which raised $25bn in 2014 in New York.
Rocky road to market
It came after a testing journey for Aramco's public offering.
Saudi Arabia had to rely on domestic and regional investors to sell the 1.5% stake after lukewarm interest from abroad.
It initially sought to raise $100bn on two exchanges - with listings on the Saudi Stock Exchange, or Tadawul and an overseas market.
The plan was scaled back after foreign investors raised concerns about climate change, political risk, and a lack of corporate transparency.
International institutions were also unconvinced by the firm's valuation, prompting Aramco to pull marketing events in New York and London.
Instead, it focused its efforts on Saudi Arabian investors and wealthy Gulf Arab allies. Saudi banks also offered citizens cheap credit to buy the shares following a nationwide advertising campaign.
The share sale is at the heart of plans to modernise the Saudi economy and wean it off its dependence on oil.
The kingdom urgently needs tens of billions of dollars to fund megaprojects and develop new industries.