Black Flag

Black Flag is a virtual accelerator and pre-seed investor for founders building critical technologies for American national security, structured as a program for founders ready to change the tides of American innovation for future generations. It launched in 2025 as an initiative of Harpoon Ventures, the San Diego defense venture firm started by former Navy SEAL and Olympic medalist Larsen Jensen, and takes applications on a rolling monthly batch cycle.

The offer is a first check of $250,000 to $1 million, with up to $5 million available through the wider Harpoon relationship, paired with direct access to defense buyers including DARPA, the Defense Innovation Unit, the military branches and the Department of Energy. Black Flag can lead rounds and negotiates valuation and terms company by company rather than imposing standard accelerator terms, and the program has no fixed start or end date, so support continues past the initial milestones.

Its most distinctive mechanic is the shared application: one submission is reviewed simultaneously by three specialized defense investors, Black Flag, Shield Capital and In-Q-Tel, collapsing what is normally three separate fundraising processes into one. Sector coverage spans aerospace, defense, deeptech and hardware, energy, artificial intelligence, manufacturing, cybersecurity, robotics, semiconductors, materials science and health and biology. Named portfolio companies include Type III, Tectonic Labs, EraDrive and Super Powers Mobility, alongside several undisclosed teams working on AI-powered mineral exploration and autonomous submersibles. The program runs virtually, with team members in Southern California, Seattle and Colorado available for in-person work.