What brand of knife do Navy SEALs use?

There is no single knife brand used by every Navy SEAL, but the Ontario Mark 3 Navy Knife is one of the best-known standard-issues tied to US Naval forces. That makes Ontario Knife Company the closest direct response to the question. In real use, SEALs are not limited to one universal brand for all missions, and privately chosen knives can include other makers such as SOG or Benchmade depending on the role. Mission type, gear setup, and personal preference matter.