Series B funding hits $48 billion in 2026 as AI startups dominate

In 2026, US investors put roughly $48 billion into funding around the Series B stage. The figure comes from Crunchbase. It is the highest level in years. Series B funding in 2026 tells the story of a divided market. The number of rounds is below 2025 levels. It is heading toward a multi-year low. Capital, in short, is concentrating on a narrow group of leading artificial intelligence startups.

More capital, fewer rounds: the Series B picture in 2026

The starting point, according to Crunchbase, is a growing but increasingly selective flow of capital. The apparent contradiction between more money overall and fewer deals has a precise explanation. Amounts are piling up on a few large deals, especially in the AI segment. Mid-sized and small rounds are becoming progressively rarer.

Small rounds decline, mega-rounds boom

The concentration is best measured by looking at the distribution of deal sizes. In 2026, less than a third of the deals in the sample analyzed by Crunchbase are below $30 million. Between 2021 and 2025, such rounds accounted for roughly half of all deals. The smallest Series B rounds have been cut the most: only 26 rounds below $10 million have appeared so far in the sample.

On the opposite side, very large rounds remain the protagonists. At least 110 companies have raised $100 million or more around this stage, or about a quarter of all deals. The largest round amounts to $12 billion for Prometheus. The physical AI startup was founded by Jeff Bezos. It has not publicly announced the close as a Series B, but multiple outlets, including Axios, describe it as such.

Behind Prometheus, two companies stopped at the $1 billion mark. World Labs, led by AI pioneer Fei-Fei Li, closed its round in February. Nuclear energy startup Valar Atomics obtained the same amount in tranches, with Sequoia Capital as lead investor.

A story mostly about AI

Crunchbase’s analysis confirms that the group of Series B beneficiaries is heavily oriented toward artificial intelligence. About two-thirds of Series B funding in 2026 went to AI-focused startups, compared with roughly half in 2025. The figure also holds by deal count: in 2026, more than half of all US Series B rounds reported involve AI companies.

A favorable climate, but only for some

According to Crunchbase’s analysis, the numbers point to a bullish climate for Series B funding, particularly for AI startups with demonstrated traction. The environment appears especially favorable to companies that have already raised substantial amounts in earlier rounds, between seed and Series A. These are not the best times for startups seeking small rounds. In the current AI-driven cycle, investors are increasingly betting on large checks. Highly valued companies are the preferred choice.

Sources:

• Series B Funding Is Up, But Fewer Deals Are Getting Done | news.crunchbase.com