Cognition refers to a mental action of acquiring and processing of information. The cognitive capacity of an individual organism is tightly tied to its evolution. Humans and animals have evolved certain skills that help us to acquire the resources needed to survive, thrive and reproduce. Cognitive processing is energetically demanding; thus, unless there is an evolutionary benefit, complex cognition is hypothesised to be detrimental to survival. With this in mind, we can view animal cognition in a different light. Both the existence and absence of a cognitive skill are a reflection of the evolution of a species. Sheep receive a lot of poor press for being stupid or dim. They may well be the ultimate prey species: their primary defence strategy is to group together or take flight. As a result, they are very alert, and can be easily fearful and distressed, all of which influences their cognition and behavioural reactions. They are also stoic by nature and so it is not easy to see if they are experiencing negative or positive affective states. They are, however, exceptionally flexible and adaptable. They can be found in the wild in Asia, Europe and North America, and domestically across all continents. Sheep are used in medical research, and are farmed in large numbers, intensively and extensively, and used for milk, wool and meat. Succeed in such diverse situations, they require a significant degree of cognitive flexibility. This chapter details what we currently know about the cognitive abilities of sheep, and how we can use that information to improve the way they are managed.