The World Cup sends prediction market volumes soaring to record highs

The 2026 FIFA World Cup was forecast to be the biggest gambling event in history. For prediction market platforms, that's led to soaring trading volumes in June. Kalshi saw more than $31 billion in notional volume during the month, a more than 70% increase from May's total of $17.9 billion, according to user collected data on Dune Analytics. The platform has consistently managed volume over $1 billion daily since the soccer tournament began on June 11. Polymarket's international event contract exchange set a new record high in monthly volume, with notional trading exceeding $10.8 billion in June. That reverses a downtrend in April and May, when volume fell. Meanwhile, Polymarket's U.S. platform did north of $3.5 billion in notional volume during the month, up from $1.77 billion in May. Team USA Monday Team USA is set to play Belgium in the round of 16 on Monday night. More than $64 million on Kalshi and $122 million on Polymarket has been traded on whether the U.S. will win the tournament, though odds of that happening are just 4.3% and 3%, respectively, on each platform. World Cup enthusiasm has given a jolt to prediction market platform Rothera, a joint venture between Susquehanna International Group and Robinhood. Rothera debuted in June, when Robinhood began routing certain World Cup contracts on its brokerage to the platform. Rothera saw $2 billion in notional trading volume during the month, and now accounts for 7% of U.S. prediction market volume, according to Bank of America. All platforms leaned into the World Cup to boost traffic. Polymarket launched a competition to reward up to $2 million to whoever can craft a perfect World Cup knockout round bracket. On the Apple app store, Kalshi boasted that users can "Trade the World Cup" in the title of its mobile platform. Heightened open interest — the total number of active, unsettled contracts on the platforms — may also reflect World Cup excitement. Kalshi open interest is now above $1 billion. Polymarket open interest is just under $400 million — elevated, but about where its international platform has been for the last few months. Sports were the focus last month for event contract exchanges, but how the platforms handled the surge in volume may be a sign of how they manage other contract topics in the future. Asaf Meir, CEO at Solidus Labs — a market integrity company that has a partnership with Kalshi — said the World Cup is a key moment for platforms as both regulators and institutions are eying how they perform. Outside observers are asking, "Is it safe enough? Is it mature enough? Does it have enough volume?," Meir said. "The World Cup is such a huge pressure test to see whether indeed prediction markets are able to deliver their word on maintaining a level playing field for all investors for a long period of time in a sustained high-volume environment." Disclosure: CNBC and Kalshi have a commercial relationship that includes customer acquisition and a minority investment.