The global landscape of Mars is diverse, and this diversity tells a story of its surface history. Geographic regions and zones, each unique in character, are dominated by specific landforms and materials. These in turn express processes and histories, including geologic and climate-driven activity. Understanding the major geographic regions of Mars, as on Earth, then, is essential to unraveling the factors involved in global and regional geologic activity. It also provides context for study of local areas and individual features or sets of features. In addition, some of the major regions of Mars are indicative of heterogeneities in the crust and mantle (see Chapter 5).