LMArena Raises $200M Series B at $3.1B Valuation, Launches Alignment Index

Arena (LMArena), the AI model evaluation battle platform, has closed a $200 million Series B round at a post-money valuation of $3.1 billion, with annualized revenue topping $100 million and a new benchmark, the Alignment Index, released alongside. The deal signals that model evaluation is rapidly rising in commercial value within the AI ecosystem.

Confirmed

The round totals $200 million at a $3.1 billion valuation, co-led by Lightspeed and Khosla Ventures, with participation from Salesforce Ventures, a16z, Felicis and others (per @arena's official post).
Annualized revenue has surpassed $100 million; the platform has facilitated 350 million cumulative sessions and 62 million votes, making it one of the world's largest model evaluation communities.
Alongside the funding, Arena launched the Alignment Index, positioned as a neutral third-party benchmark measuring AI safety and alignment in real-world use, initially covering 20+ frontier models.
The Alignment Index is built on real-world agent usage trajectories and debuts with three signal categories: unauthorized actions, false attribution, and deceptive task completion.
Felicis published a long-form piece recounting founders Anastasios Angelopoulos and Wei-Lin Chiang's journey: in spring 2024 the two were still Berkeley PhD students, and they since grew the project into a company valued at $3.1 billion.

Why it matters

The $3.1 billion valuation and nine-figure annualized revenue show that community-vote-driven model rankings have evolved from an academic project into a category with a scalable business model, with top-tier VCs backing the leading player.
The Alignment Index turns "alignment and safety" from a vague vendor promise into a quantifiable third-party signal; if adopted industry-wide, it could shape model procurement and regulatory discourse.

2026-10-09 ~ 2026-10-09 · 9 related posts

Primary sources

Arena Raises $200M Series B at $3.1B Valuation, Tops $100M Annualized Revenue — arena · 2026-10-09 00:07 (UTC+08:00)
LMArena raises $200M Series B at $3.1B valuation, launches Alignment Index — arena · 2026-10-09 01:15 (UTC+08:00)
Felicis Profiles Arena's Journey: From Berkeley PhD Project to $3.1B Valuation — pxd · 2026-10-09 00:39 (UTC+08:00)

[source] Arena Raises $200M Series B at $3.1B Valuation, Tops $100M Annualized Revenue — arena · 2026-10-09
Arena raises $200M Series B at $3.1B valuation, launches agent Alignment Index — a16z · 2026-10-09
[source] Felicis Profiles Arena's Journey: From Berkeley PhD Project to $3.1B Valuation — pxd · 2026-10-09
AI Model Ranking Platform Arena Hits $3.1 Billion Valuation in New Funding Round — Polymarket · 2026-10-09
Arena raises $200M Series B at $3.1B valuation, launches Alignment Index — jfiance · 2026-10-09
[source] LMArena raises $200M Series B at $3.1B valuation, launches Alignment Index — arena · 2026-10-09

3 near-duplicate retellings: infwinston · pxd · jfiance