OpenAI’s $852 billion valuation from its March 2026 funding round, backed by massive commitments from investors including SoftBank, Nvidia, and Amazon, positions it as the clear second-largest private company behind Anthropic’s $965 billion mark. Strong revenue growth nearing a $70 billion annualized run rate, continued large language model advancements, and secondary market activity reinforce trader consensus that OpenAI leads the listed options at end-September 2026. A new $1.4 trillion pre-IPO round in active discussion further cements this standing. Realistic challenges include a sharp downward revaluation of OpenAI’s tender or secondary marks, an upward adjustment for ByteDance or Databricks, or unexpected regulatory or competitive shifts altering relative valuations among top AI labs.