River Markets announced Tuesday that it has raised $8.5 million in a seed round led by Haun Ventures that closed in July to build trading tools for prediction markets aimed at professional traders and institutions. The round included participation from Y Combinator and Coinbase Ventures, institutional backers such as Qube Research Technologies, and angel investors who work at Google, Nvidia, Novig, JPMorgan and Citadel. Co-founders Oscar Levy (CEO) and Antonin Parrot (CTO) declined to specify the valuation at which the capital was raised.
The startup says its platform gives professional traders a single place to trade across multiple prediction markets, addressing what its founders describe as a fragmented landscape of separate venues. Since launching in May, River Markets has provided software, data links and risk-management tools that let firms trade across platforms and handle larger orders, while algorithms aim to limit price swings caused by big trades. Levy said the platform is on track to exceed hundreds of millions of dollars in annualized trading volume by year-end.
“This transition from mainstream retail to institutional can’t really be achieved with today’s consumer interfaces. That’s [why] somebody like us needs to come in and spend the time to make these accessible and familiar for all of these existing institutions and large traders,” Levy said.
Building for institutional prediction markets
Levy and Parrot met as students at UC Berkeley, bonding over poker games and nights trading Japanese stocks. After graduation they worked in quantitative trading: Levy became a vice president and quantitative specialist at BlackRock, working on multibillion-dollar portfolios, while Parrot focused on electronic trading at Morgan Stanley before becoming a quantitative researcher in high-frequency trading at Valkyrie Trading.
The pair conceived River Markets in 2023. While working full time, they spent weekends building trading software for platforms such as Kalshi and Polymarket; the technology generated seven figures in trading profits and was adapted into an enterprise platform. Their own trading highlighted a core problem: the market is split across separate exchanges, and even when two platforms offer contracts on the same event, traders cannot easily manage them together. The founders estimated most firms would need six to nine months to build equivalent software from scratch, which propelled them to productize their tool as River Markets.
“They have this ability to speak both to this esoteric market language and… solve the problems that traders are facing today in prediction markets, but they’re [also] thinking about it in a way that is informed by the experience they had building traditional trading tech,” said Mark Beylin, an investor at Haun Ventures.
The fundraising comes as institutions increasingly treat prediction markets as financial tools. Kalshi said in May that institutional trading volume on its exchange had increased 800% over the previous six months. The shift has enabled large, privately negotiated block trades: in April, Kalshi completed a block trade for a Houston environmental hedge fund seeking exposure to the outcome of a California carbon-allowance auction, and in June Polymarket completed a similar block trade tied to GPU-rental prices so a firm could hedge computing-cost exposure.
River Markets plans to use the new capital to hire engineers, build faster and more secure trading systems, expand its sales and operations teams as it signs professional clients, and develop tools to help institutions manage money and trade at larger scale across prediction markets.
