Alphabet’s shares surged by more than 4% during Monday trading, pushing the tech giant past the landmark $3 trillion cap. The rally comes after a decisive U.S. court ruling allowed Alphabet to retain control of key assets including its Chrome browser and Android operating system, two linchpins of its global enterprise that had been at risk due to regulatory challenges. This antitrust victory eliminated concerns over a potential breakup, boosting investor confidence at a pivotal time.

Fueling the ascent is Alphabet’s aggressive investment in AI, most notably through the Gemini AI model, now integrated across Google’s search, advertising, and cloud products. Other growth streams—including Workspace, YouTube Shorts, and proprietary chips—have further diversified revenues and reinforced perceptions of Alphabet as a multidimensional technology leader, not merely a search and advertising company.

With shares up over 32% year-to-date, Alphabet is 2025’s best-performing member of the so-called “Magnificent Seven,” outpacing the S&P 500’s 12.5% gain. Its multi-pronged AI strategy has cemented Alphabet as a cornerstone of the tech-driven economy at a time when investors are seeking resilient, innovation-centric companies.

Who’s in the $3 Trillion and $4 Trillion Club?

Alphabet now stands alongside only a handful of mega-cap peers in the $3 trillion echelon. The club includes:

Six more companies are above the $1 trillion mark, including tech firms Amazon and Meta, semiconductor firms Broadcom and TSMC, the national oil giant Saudi Aramco, and Warren Buffett’s famous conglomerate Berkshire Hathaway.

This surge in market valuation comes amidst a wave of technological and economic transformations:

AI Leadership: Progress in AI, including models like Alphabet’s Gemini, Nvidia’s specialized chips, and Microsoft’s Copilot in Azure, is attracting huge investor inflows.Legal Clarity: Alphabet’s victory in U.S. court resolved major antitrust overhang, allowing continued integration of Chrome and Android and solidifying confidence in long-term growth.Investor Sentiment: With economic uncertainty, capital is flowing to companies perceived as innovation leaders resilient to downturns, further elevating market caps at the very top.

On this last point, Fortune‘s Shawn Tully reported that the S&P 500 has a distinctly bubbly price to earnings ratio of 29.85x, a number seldom mentioned by Wall Street analysts or pundits. Apollo Global Management’s chief investment strategist Torsten Slok has looked at the trillion-cap club and found the S&P 500 to be so remarkably concentrated that the top 10% of stocks contribute 54% of market returns since January 2021.

For this story, Fortune used generative AI to help with an initial draft. An editor verified the accuracy of the information before publishing.