Thirdbase Capital

Thirdbase Capital is a New York-based private markets firm investing in the growth-stage leaders of frontier AI, defense, energy, robotics, and more. It concentrates most of its capital in a handful of companies it has spent years understanding. The firm invests through three tracks: direct investments at Series B and beyond, strategic access to late-stage leaders through bespoke transactions, and early capital for emerging managers and founders at the seed and Series A stages. A co-investment platform lets aligned investors join specific high-conviction opportunities. Areas of interest include physical AI and autonomy, AI infrastructure, frontier AI, cybersecurity, defense and aerospace, and critical minerals and energy. Portfolio companies include OpenAI, Anduril, Databricks, Perplexity, Saronic, Crusoe, Kalshi, Aalo Atomics, and Abridge. The firm seeks companies where capital, timing, and conviction converge and that are positioned to define their decade.