Arena Raises $200M Series B at $3.1B Valuation

What happened

The round was led by Lightspeed and Khosla Ventures, with participation from a16z, Salesforce Ventures, and others. Arena also disclosed annualized revenue above $100 million.

Alongside the raise, Arena launched the Alignment Index, a new metric for how well AI systems align with human values and safety.

Key facts

1. Raise and valuation:$200M Series B at a $3.1B post-money valuation.
2. Investors:led by Lightspeed and Khosla Ventures, with a16z, Salesforce Ventures, and others participating.
3. Business base:spun out of Berkeley's LMSYS project (the origin of Chatbot Arena); now tracks 1,000+ open and closed models with ARR above $100M.
4. New product:the Alignment Index, measuring AI safety and alignment with human values.