Prediction market platform Kalshi has entered into an exclusive partnership with the U.S. Tennis Association to become the US Open's official prediction market platform partner, according to Front Office Sports. The agreement took effect immediately after being finalized following the tournament's qualifying rounds, and financial terms were not disclosed.
The deal designates Kalshi as the tournament's sole prediction market partner and prohibits competing prediction market platforms from advertising at the US Open venue and across tournament television coverage, including ESPN broadcasts. The report cited two people familiar with the agreement.
Negotiations in recent weeks had involved multiple prediction market platforms and initially focused partly on match integrity and potential partnerships beginning next year. Plans changed after Craig Tiley took over as USTA CEO on July 20, with Tiley playing a major role in pushing for an agreement covering the 2026 tournament.
Kalshi already offers a large number of contracts tied to US Open matches. Its tennis markets on Sunday included individual men's and women's singles matches, with some contracts recording more than $1 million in trading volume. The partnership had not yet been fully reflected across public materials as the main draw started Sunday, and a Kalshi blog post still carried a disclaimer saying the company was "not affiliated with the U.S. Open or WTA."
The US Open agreement expands Kalshi's sports strategy. In June, Kalshi secured World Cup branding exposure through a partnership with ADI Predictstreet, FIFA's official prediction market partner for the 2026 tournament. Kalshi and Polymarket have partnerships with the NHL, while Kalshi has also announced relationships with several MLB clubs. Sports-related contracts have become Kalshi's largest product category, with weekly trading volume reaching a record $5.1 billion in June.
Kalshi has developed compliance systems alongside its expansion, including IC360 screening, a prohibited-persons system, its proprietary Poirot detection engine, and Solidus Labs' HALO surveillance platform.
The commercial push continues while courts consider whether sports event contracts offered on federally regulated prediction markets can remain outside state gambling regimes. Two days before the US Open partnership emerged, the Ninth U.S. Circuit Court of Appeals ruled on Aug. 28 that Kalshi had not shown the Commodity Exchange Act was likely to preempt Nevada gaming regulations for its sports event contracts. The court found the contracts did not qualify as swaps under the relevant definition because they were sports bets.
Kalshi has faced conflicting rulings. The Third Circuit previously upheld preliminary relief preventing New Jersey regulators from enforcing state gambling laws against its sports contracts, while a federal judge in New York rejected Kalshi's injunction bid in July. Baltimore also sued Kalshi and Polymarket on Aug. 13 over alleged unlicensed sports betting, with the Kalshi complaint naming Coinbase, Robinhood and Webull because those platforms distribute its event contracts.
