The US Open has reportedly signed Kalshi as its exclusive prediction market platform partner. The agreement with the US Tennis Association (USTA) took effect immediately and was only formally completed after last week's US Open qualifying rounds, Front Office Sports reported.
The USTA initially planned to explore prediction market partnerships for 2027 and beyond, and discussions reportedly included concerns around match integrity. However, new USTA CEO Craig Tiley played a big role in securing a partnership in time for this year's tournament.
One particularly interesting part of the agreement is its exclusivity. According to FOS, the USTA is preventing competing prediction market platforms from advertising at the US Open venue or during television coverage, including ESPN broadcasts.
The deal came together so quickly that signs of the previous situation were still visible when the US Open main draw began. Kalshi was not listed among the tournament's official partners Sunday afternoon, while a Kalshi article covering the women's singles competition still carried a disclaimer saying the company was not affiliated with the US Open or WTA.
So far, roughly $1.6 million has already been traded on Kalshi's women's singles winner market by early Monday morning.
(Source: Kalshi)
Kalshi's Sports Expansion Accelerates
The US Open partnership extends an aggressive push by prediction markets into mainstream sports.
Just days earlier, Kalshi announced partnerships with five MLB teams: the Boston Red Sox, Los Angeles Dodgers, San Diego Padres, Atlanta Braves and San Francisco Giants. Kalshi said baseball trading volume on its platform has increased 36-fold year over year.
The expansion comes despite major uncertainty over how sports prediction markets should be regulated. On Friday, the Ninth Circuit Court of Appeals ruled that Nevada can enforce its gambling laws against Kalshi's sports event contracts. That conflicts with an earlier Third Circuit decision preventing New Jersey from doing the same.
For now, however, sports organizations are still moving into the sector. Kalshi and Polymarket already have NHL relationships, while Polymarket has an MLB-wide agreement and partnerships across several other major sports competitions.
The US Open deal suggests tennis is now becoming another major battleground in the prediction market industry.