OpenAI · Series B

Creator of ChatGPT, GPT-4, and the leading frontier AI lab.

Amount

$10.3B

Round

Series B

Valuation

$157B

Announced

Oct 2025

Investors

Lead investor

Participating investors

M12 — Microsoft's Venture Fund

Notes

Largest private funding round in history

Other OpenAI rounds

Date	Round	Amount
Mar 2026	Series E	$122B	Details →
Mar 2025	Series D	$40B	Details →
Jan 2024	Series A	$10B	Details →
Jan 2023	Series C	$10B	Details →
Jan 2021	Series B	$1B	Details →
Jul 2019	Series A	$11M	Details →