River Markets raises $8.5M seed round to build Wall Street-grade tools for prediction markets

Prediction markets have spent the last couple of years graduating from niche curiosity to legitimate financial infrastructure. River Markets, a San Francisco-based startup, just raised $8.5M in seed funding to accelerate that transition by giving hedge funds and prop trading firms the kind of execution tools they’re used to in traditional markets. The round was led by Haun Ventures, with participation from Y Combinator, Coinbase Ventures, and institutional backer Qube Research Technologies. Angel investors from Google, Nvidia, Novig, JPMorgan, and Citadel also chipped in. The round closed in July. A prime brokerage for event contracts River Markets is essentially building the prime brokerage layer that prediction markets never had. The platform aggregates access to multiple venues, including Kalshi, Polymarket, Polymarket US, and Novig, into a single account. The feature set includes smart order routing, iceberg orders, advanced order types, and unified portfolio management across venues. The company says it has already facilitated over $50M in trading volume. It also claims to support three of the top 10 traders on both Kalshi and Polymarket. The fragmentation problem River Market...