#38 Aggregator
River Markets
Prime brokerage for prediction markets: a professional execution stack with multi-venue OMS, smart order routing, native algos, and Python SDK across Polymarket and Kalshi.
$ 5.25M 1m volume
Quick facts
- Team
- 1-10
- Funding
- YC (self-reported)
- Y Combinator (self-reported)
- Pricing
- Unknown (institutional / desk-targeting) · $0/mo
- Chains
- Polygon
- Venues
- Polymarket · Kalshi · Polymarket US (coming soon) · Novig (coming soon) · Rothera (coming soon)
Stats across DAY · WEEK · MONTH · ALL
From the Polymarket public data API. Updated daily.
Today · 24h
#121
$75
2 active users
This week · 7d
#143
$90
2 active users
This month · 30d
#90
$79.9k
11 active users
All-time · all
#38
$5.25M
27 active users
builderCode
The 32-byte hash Polymarket uses to attribute volume to this builder on-chain.
0x4b649086188c89c3ab20da88f7dd568b3e078159bd026d286c43b719e3b568e6 What is River Markets?
River Markets is a Trading Tool for Polymarket positioned as 'prime brokerage for prediction markets' — offering professional execution, position management, and P&L tooling wired to every venue desks use. The platform supports Polymarket and Kalshi live today, with Polymarket US, Novig, and Rothera 'coming soon.' Core features include a multi-book OMS managing hundreds of orders simultaneously, native execution algorithms (Icebergs, Pegs, server-managed Take-Profit and Stop-Loss orders), smart routing that delivers an average 2¢ price improvement across venues, subaccount isolation for strategies and capital, Ed25519-signed local authentication, and an official Python SDK with both sync and async clients. River Markets is self-described as backed by Y Combinator and lists Chimera Capital Management, Game Point Capital, and Cleat Street among trusted partners. As of May 2026 it ranks #90 on the 30-day Polymarket Builders leaderboard with $79.9k routed from 11 monthly users, and #38 all-time at $5.25M cumulative volume from 27 wallets.
River Markets pitches itself as 'prime brokerage for prediction markets' — a professional execution stack purpose-built for prediction-market desks. The product gives traders a unified OMS across Kalshi and Polymarket from a single blotter, with standardized 'river_id' identifiers normalizing market references across venues. Smart order routing delivers an average 2¢ price improvement on cross-venue executions, and subaccount isolation lets desks segregate strategies and capital cleanly.
Native execution algorithms include Icebergs (size-hiding), Pegs (passive-bid), and server-managed Take-Profit / Stop-Loss orders that survive client disconnection. Authentication uses Ed25519-signed local keys (a step above conventional API-key models), and the official Python SDK ships both synchronous and async clients. Coming-soon integrations announced on the site cover Polymarket US, Novig, and Rothera — implying ambition to be the institutional aggregation layer for the entire US-regulated prediction-market venue set.
River Markets is backed by Y Combinator (the site states 'Backed by Y Combinator'; the company is not yet listed on the public YC directory under the River Markets name as of May 2026, so this is a self-reported claim awaiting independent confirmation). Trusted-partner logos on the homepage include Chimera Capital Management, Game Point Capital, and Cleat Street — all professional trading desks, which fits the institutional positioning. Founders are not disclosed on the marketing site, and X account @river_markets is the primary off-site channel (X.com profile fetch returned HTTP 402, so follower counts are not available).
On the Polymarket Builders leaderboard, River Markets is a low-frequency / high-ticket integration: just 11 monthly active users routing $79.9k (#90 on the 30-day list) but $5.25M cumulative volume from 27 lifetime wallets (#38 all-time). The 27-user cumulative wallet count alongside $5.25M routed implies very large average tickets per user — consistent with an institutional desk-targeting product rather than a retail trading interface.
Key features
- Multi-book OMS across Polymarket and Kalshi
- Smart order routing (~2¢ avg price improvement)
- Native algos: Icebergs, Pegs, server-managed TP/SL
- Standardized river_id identifiers across venues
- Subaccount isolation for strategies and capital
- Ed25519-signed local authentication
- Official Python SDK (sync + async)
Funding & investors
- Stage
- YC (self-reported)
- Investors
- Y Combinator (self-reported)
- Announcement
- https://www.rivermarkets.com/
What others have written about River Markets
- River Markets — Prime Brokerage for Prediction Markets — Official site
Rank + volume over time
Daily snapshots from our scraper. Charts populate as history accumulates.
All-time rank
Lower is better. Inverted Y-axis.
All-time volume
Cumulative routed volume in USD.
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How to verify River Markets
- On-chain attribution — every Polymarket Builder routes via an order that includes their
builderCode. The hash above is checkable on Polygon against Polymarket's CTF Exchange. - Polymarket's own verification — $River Markets carries the official ✓ verified flag in the data API.
- Cross-check Polybot Arena — polybot.arena tracks wallet-level P&L for builder-tagged bots. If a builder claims specific performance, their wallet should be findable there.
- Tier-2 patterns to avoid — we flag builders that match the Tier-2 pattern (no public team, no verifiable claims, recurs across affiliate-SEO listicles). See our /methodology page for the full criteria.
About River Markets 07 answers
FAQ
01 What is River Markets?
River Markets is a Trading Tool for Polymarket positioned as 'prime brokerage for prediction markets' — offering professional execution, position management, and P&L tooling wired to every venue desks use. The platform supports Polymarket and Kalshi live today, with Polymarket US, Novig, and Rothera 'coming soon.' Core features include a multi-book OMS managing hundreds of orders simultaneously, native execution algorithms (Icebergs, Pegs, server-managed Take-Profit and Stop-Loss orders), smart routing that delivers an average 2¢ price improvement across venues, subaccount isolation for strategies and capital, Ed25519-signed local authentication, and an official Python SDK with both sync and async clients. River Markets is self-described as backed by Y Combinator and lists Chimera Capital Management, Game Point Capital, and Cleat Street among trusted partners. As of May 2026 it ranks #90 on the 30-day Polymarket Builders leaderboard with $79.9k routed from 11 monthly users, and #38 all-time at $5.25M cumulative volume from 27 wallets.
02 What is the official website of River Markets?
River Markets's official site is https://www.rivermarkets.com/. We verified the URL by visiting the homepage and confirming it references Polymarket or prediction markets directly. If you believe this URL is incorrect, email [email protected].
03 Is River Markets verified by Polymarket?
Yes — River Markets carries Polymarket's official ✓ verified flag (returned by their data API as `verified: true`). This indicates Polymarket has reviewed the builder; it's not a guarantee of product quality or financial outcomes.
04 Has River Markets raised funding?
YC (self-reported); $0K raised; investors include Y Combinator (self-reported). Announcement: https://www.rivermarkets.com/.
05 How much does River Markets cost?
pricing model: Unknown (institutional / desk-targeting); paid plans from $0/month; Pricing not publicly disclosed; institutional positioning suggests bespoke contracts.. Sourced from the official site at the time of research; verify the current pricing on the builder's website before subscribing.
06 What are River Markets's key features?
Multi-book OMS across Polymarket and Kalshi; Smart order routing (~2¢ avg price improvement); Native algos: Icebergs, Pegs, server-managed TP/SL; Standardized river_id identifiers across venues; Subaccount isolation for strategies and capital; Ed25519-signed local authentication; Official Python SDK (sync + async). Sourced from the official site/homepage at the time of research.
07 How does River Markets compare to similar builders?
River Markets is ranked #38 all-time, with similar-category peers including traderline, Matchr.xyz, NoArb. The leaderboard reorders daily — see the history chart for River Markets's rank trajectory.