US venture capital funding hits $18.1B in August driven by AI megadeals

US venture capital activity in August 2026 saw a significant surge in capital deployment despite a decline in total deal volume. Startups raised $18.1 billion across 333 deals, representing a 123% increase in capital compared to August 2025. This growth was driven by a concentration of megadeals in sectors such as defense technology, clean energy, and AI infrastructure. Notable late-stage rounds included River AI’s $1.1 billion Series A, Base Power’s $1.0 billion raise, and Castelion’s $800 million round.

In a related movement within the AI sector, Bain Capital Ventures closed its Fund XI at $1.6 billion. This fund is specifically targeted at early-stage AI companies, focusing on four key verticals: AI infrastructure, physical AI (robotics and automation), security, and applications. The fund size marks an increase from its predecessor, Fund X, which raised $1.4 billion in 2023.