Here we present the design of a topological array trigger for the Cherenkov Telescope Array (CTA), a next generation ground-based very high energy gamma-ray observatory. CTA will have improved sensitivity, cover a broader energy range, and posses a wider field of view than the current generation of imaging atmospheric Cherenkov telescopes. The array will consist of up to 100 telescopes, of three different sizes, spread over an area of approximately one square kilometer. A topological array trigger is a powerful tool for reducing and stabilizing the high trigger and data rates associated with CTA. The large scale of CTA also makes it well suited for applying a realtime (hardware) array trigger in a decentralized fashion.