Gut function and health are pre-requisites for sustainable poultry production and product quality. Phytogenics are bioactive components of plant origin that can protect poultry from the detrimental effects of modern stressor challenges in intensive farming systems via the enhancement of gut integrity, induction of adaptive cytoprotective capacity and the beneficial management of inflammatory response. This chapter covers the use of phytogenics in optimising gut function and health in poultry. It begins by reviewing the main types of phytogenic compound (terpenoids, flavonoids and alkaloids) as well as general issues relating to phytogenic variability and bioavailability. Following sections review relevant aspects of poultry gut function, particularly critical signaling pathways and gene components that are directly linked to optimal gut function and health. The chapter will then discuss the beneficial effects of phytogenics in the maintenance and protection of gut function and health, focusing particularly on gut barrier integrity, cytoprotection and inflammatory response.