Anthropic, the AI safety startup founded by former OpenAI researchers, has closed a $2 billion Series D funding round at an $18 billion valuation.

Google led the round, increasing its total investment in the company to $4 billion. Spark Capital and new investor Menlo Ventures also participated.

The funding comes as Anthropic's Claude AI assistant gains traction in the enterprise market, competing directly with OpenAI's ChatGPT and Microsoft's Copilot.

Anthropic has differentiated itself by emphasizing AI safety and developing "constitutional AI" techniques to make its models more helpful and harmless.