Zero Day Brokers is an underground consulting and brokerage company based in Mountain View, CA. It is most notable for its connections to the GreyHat hacking community around the world. 

The company reached notoriety when it represented a number of Albanian hacker groups through negotiations with Apple and Microsoft regarding zero day bugs. The amount exchanged for the information was never made public, nor have any members of either group come forward. Despite this, Zero Day Brokers has become one of the only public facing channels between hackers and corporations.