SpaceX or Anthropic: Which Will Have the Highest IPO Market Cap in 2026?

• Polymarket prices NO shares at 58% while Yes trades at 42%.
• This market has recorded $848.2K in trading volume, with $4.6K traded in the past 24 hours.
• Liquidity currently stands at $27.3K, representing the available capital across the market.
• The market will resolve on December 31, 2026

Overview

The market “Largest IPO by market cap in 2026?” on Polymarket has seen a huge shift in the past three days, as Anthropic rose as a capable challenger to SpaceX’s almost sure win. At the start of August, Polymarket traders priced SpaceX being the largest IPO in 2026 at 94 cents. However, the certainty flipped following Anthropic’s S-1 filing to the SEC, claiming the 20% SpaceX lost as its own. 

As of writing, traders are pricing Anthropic’s IPO at 26.8% to top the charts, while SpaceX’s probability is at 71%. 

According to the resolution rules, the winner is whichever company completes an IPO between January 1 and December 31, 2026, and finishes its first trading day with the highest market capitalization (dollar value), measured as shares outstanding times the closing price and sourced from the primary exchange’s listing page.

As of August 14, the market has traded $694,037 in lifetime volumes, $86,916 inflowing in the past 24 hours, and $54,061 available in open interest. The remaining 2.2% is shared across 10 companies that have launched (or are reported to launch) an IPO this year, including OpenAI, Discord, ByteDance, Stripe, Kraken, SHEIN, Waymo, Revolut, Perplexity AI, and Databricks.

Why SpaceX Still Leads at 71%

According to experts, Anthropic is rumored to hit a $2 trillion valuation at the launch of its IPO in October, which could exceed SpaceX’s $1.77 trillion opening, hence a section of the market believing the crown will change hands. However, this is not explicit in what the contract rules state. 

For Anthropic to win this market, it will need to clear SpaceX’s first session close at $2.1 trillion, given SpaceX’s heroics on the first day – climbing 20% to close at $161 from an opening of $135. The closing number is the one that resolves this market. Anthropic’s opening valuation at $2 trillion does not settle anything on its own, as it would need a pop of about 5% on day one to overtake SpaceX. 

SpaceX’s stock currently sits near $142 for a market cap around $1.85 trillion, well off the $225 June high, and it only reclaimed the $135 IPO price this week after the 911.5 million-share lockup expiry. However, none of this matters for this market, as only the first day of trading counts. 

Is Anthropic Being Underpriced at 26.8%?

Having filed its S-1 confidential report to the SEC on June 1, just four days after closing a $65 billion Series H at a $965 billion valuation, could the Polymarket traders be undervaluing Anthropic’s potential win?

According to reports from the Financial Times, backers of Anthropic expect at least a $2 trillion opening valuation once it IPOs in October, making it the most valuable company on opening day. The AI giant currently projects nearly $100 billion to $120 billion in annualized revenue in December, which will have nearly tripled its May 2026 annualized revenue, which stood at $47 billion. 

However, the October launch date gives Anthropic very little room for anything to go wrong before the IPO date. A public S-1, a roadshow, and a priced deal all have to land inside ten weeks, and any slip into 2027 would give SpaceX a clear runaway win. OpenAI, the only other big challenger to the two, saw its odds reach 5% following its own S-1 filing in June, but has since collapsed to below 1%, given recent comments by Sam Altman that seem to confirm no IPO for the AI firm this year.