Arena raises $200M Series B at $3.1B valuation, nearly doubling worth in 10 months

Arena, the company behind the popular LMArena AI model leaderboard, has raised a $200 million Series B round at a $3.1 billion valuation, announced October 8, 2026. The round was led by Lightspeed Venture Partners and Khosla Ventures, with participation from Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z, Felicis, and others.

The new valuation represents nearly double Arena’s $1.7 billion post-money valuation from its $150 million Series A in January 2026. Over that same roughly 10-month period, the company’s annualized run-rate revenue grew from $30 million to $100 million, a figure it reported reaching in June.

Arena originated in 2023 as a research project at UC Berkeley. Its core platform is free for consumers and works by crowdsourcing AI model rankings — users submit prompts or request projects and then rate which model performs better. The company says it draws tens of millions of monthly visitors.

In September 2025, Arena launched its commercial product, AI Evaluations, which provides model labs and enterprises with detailed performance analytics drawn from community feedback. The service gained traction as AI labs discovered their models were gaming standardized benchmarks, and enterprises sought more practical guidance on which models best fit their specific needs.

“AI is advancing faster than our ability to evaluate it, and static benchmarks break down once models recognize they’re being tested,” the company said in its funding announcement. “The world needs a neutral third party to measure how safe and aligned AI actually is once it’s in the hands of real people.”

Alongside the funding news, Arena introduced a new alignment category to its leaderboard, ranking models on behaviors such as unauthorized actions, false attribution, and what it terms “deceptive completion” — lying about having completed a task. OpenAI models currently lead the preliminary alignment rankings, with Anthropic’s Claude Opus 5.5 and Claude Fable placing sixth and ninth, respectively.