Microsoft overtook Nvidia as the world’s second-most valuable listed company on Tuesday, as a sharp fall in the chipmaker’s shares reshuffled the top of the global market-value rankings for the first time since June 2025.

Nvidia shares were down more than 6% in New York trading, changing hands at around $167.11, while Microsoft shares were 0.4% lower at $543.25, according to Reuters. The move put Microsoft ahead of its rival even though both stocks were lower on the day, leaving Apple as the world’s most valuable company.

Why Nvidia shares fell

The selling in Nvidia has been driven by uncertainty over the outlook for artificial intelligence spending and by an independent board investigation into whether chief executive Jensen Huang was the target of a foreign intelligence effort. Nvidia fell 4.3% on Monday even as the wider market rallied strongly, and the decline extended on Tuesday.

Nvidia’s board announced the investigation on Sunday, saying a committee of independent directors would oversee the review with outside legal counsel. The board said it had confidence in Huang and that it had no reason to believe company secrets or national security information had been compromised. Huang has told staff he will cooperate with the investigation.

The episode has already drawn legal action. Shareholders filed a complaint in a federal court in San Jose, California, on Monday, alleging that Nvidia and Huang withheld information about the reported relationship at the centre of the scrutiny and the national security concerns it was said to raise. The claims in the lawsuit have not been tested in court.

A rapid reversal at the top

The change at the top of the rankings has come quickly. Nvidia only recently held the position of the world’s most valuable company after a long rally powered by demand for the processors used to train and run artificial intelligence systems. That rally has gone into reverse in recent sessions as investors have questioned how durable the AI spending boom will prove, and as the investigation has added a governance worry on top of a market one.

Microsoft, by contrast, has held up better through the recent pullback in technology shares. Its shares have been supported by steady demand for its cloud and software businesses, and it has avoided the sharp swings seen in the chip sector this month.

What to watch next

Investors will now look to Nvidia’s next quarterly results, due on 17 November, for a fresh read on demand for its AI chips and for any further word from the board on its investigation. Until then, the ranking of the world’s biggest companies is likely to stay sensitive to each day’s moves in the two stocks, with the gap between them narrow enough for the order to change again. Share prices quoted here are intraday figures and move during the trading session.