River Markets Raises $8.5M for Prediction Market Trading

River Markets has raised $8.5M in Seed funding to build prime-brokerage and execution infrastructure for professional prediction-market traders. Fortune reported that Haun Ventures led the round, which closed in July, with participation from Y Combinator, Coinbase Ventures, and Qube Research Technologies. The company did not disclose its valuation.

The funding matters because River Markets is not trying to create another prediction-market destination. It is building the connective tissue that lets institutions trade across venues with one terminal, shared portfolio and risk views, advanced order types, and a unified API. That is a bet on market structure: as prediction markets attract more professional capital, the infrastructure between exchanges becomes as important as the exchanges themselves.

What Happened

River Markets announced the Seed round on August 11, 2026, shortly after joining Y Combinator's Spring 2026 batch. Haun Ventures led the financing, while Coinbase Ventures and Qube Research Technologies joined Y Combinator in the syndicate. Additional angel investors from several major technology and financial firms also participated, but those individuals were not named and should remain off the public cap-table roll call.

The company plans to use the capital to hire engineers, improve the speed and security of its trading systems, and expand sales and operations. It also intends to develop tools that help institutions manage capital and trade at larger scale across prediction markets. The round therefore funds both the technical layer and the operational muscle required to sell into firms that treat execution quality, permissions, reporting, and reliability as table stakes.

The Infrastructure Gap River Markets Is Targeting

Prediction markets have grown as places to express views on elections, sports, economic releases, and other events, but the trading experience is still fragmented. Contracts tied to the same outcome can sit on different venues with different prices, ticker formats, APIs, liquidity, and operational rules. A professional desk trying to manage those markets as one portfolio can end up spending more time maintaining connectors and reconciling positions than evaluating the underlying risk.

River Markets packages that work into a prime-brokerage and execution layer. Its platform includes a multi-book terminal for orders, positions, and P&L, along with smart routing across matching contracts, subaccounts, and advanced execution such as iceberg, peg, take-profit, and stop-loss orders. The company also offers a unified REST and WebSocket API with standardized identifiers and locally signed requests, giving quantitative teams one integration surface instead of a separate engineering project for every venue.

Why the Founders Fit the Problem

CEO Oscar Levy and CTO Antonin Parrot approached the market as quantitative traders rather than consumer-app founders. They met at UC Berkeley and later worked in traditional trading environments, with Levy building quantitative models at BlackRock and Parrot working in electronic trading at Morgan Stanley before joining Valkyrie Trading. The pair began building prediction-market software on nights and weekends in 2023 before adapting their tools into an enterprise platform.

That background matters because institutional trading software is not won by adding a cleaner button to a retail interface. It requires understanding order behavior, fragmented liquidity, position management, latency, controls, and the tedious operational details that become expensive when volume rises. River Markets is selling familiarity to firms that already know what professional market infrastructure should feel like, even if the underlying asset class is new.

Traction, With the Right Qualifications

River Markets says more than $50M has traded through its platform. The company also reports 200% week-over-week growth since early April and usage by 3 of the top 10 traders on both Kalshi and Polymarket. Those are company-reported figures rather than independently audited results, so they are best read as evidence of early demand, not as a finished scorecard.

The integration map is more concrete. River Markets currently lists Kalshi, Polymarket, and Polymarket US as live, while Novig and Crypto.com are still in integration. The distinction matters because the company's value grows with reliable venue coverage, but credibility depends on being precise about what works today and what remains on the roadmap.

Why Investors Are Backing the Plumbing

The syndicate reflects several views of the same opportunity. Haun Ventures has focused on the modernization of financial infrastructure and the rise of new markets, while Coinbase Ventures brings experience backing digital-asset and trading infrastructure. Y Combinator is backing a young technical team, and Qube Research Technologies contributes the perspective of a global quantitative investment manager working across data, research, technology, and trading.

The investment case is not that every prediction market will become institutionally important. It is that a growing subset may become useful for price discovery, event-risk hedging, and systematic strategies, creating demand for tools that make fragmented venues behave more like a coherent market. Infrastructure businesses can benefit from that growth without needing to predict which single exchange, contract type, or consumer brand wins the attention contest.

What This Signals for Prediction Markets

Prediction markets are often discussed as a fight between consumer platforms, but River Markets points to a second contest underneath the surface. Exchanges can attract users and liquidity, while brokers, routing layers, data systems, and risk tools determine whether sophisticated firms can participate efficiently. When venture capital moves into those less visible layers, it signals investor conviction that the category can support more than occasional retail excitement.

The hard part now is execution. River Markets must keep venue integrations reliable, prove that its routing and controls hold up at larger scale, and earn trust from firms that do not tolerate improvisation in production trading systems. The $8.5M Seed round gives the company more room to build that foundation, but the lasting advantage will come from making cross-venue prediction-market trading feel routine, controlled, and boring in exactly the way serious financial infrastructure should.