River AI raises $1.1B Series A

River AI provides an API for fine-tuning and reinforcement learning, enabling users to build and serve personalized AI models. The company announced a $1.1B Series A on August 11, 2026, from its base in Palo Alto, US. Investors and valuation were not disclosed in Crunchbase's round record; Lounge adds them as they are reported. It has raised more than $100M in total venture funding.