The term ‘hydrocolloid’ is used to describe the polymers that perform gelling, thickening and stabilising functions in food. Most of the hydrocolloids discussed in this chapter are extracted from plants and might therefore be considered natural. However, this will depend on the degree and type of processing that they undergo post harvest. This is further complicated by consumer perception, as while additives with chemical sounding names are unpopular, hydrocolloids that have a long traditional use will usually be considered natural by consumers. In this chapter, all the different types of hydrocolloids are discussed to understand the potential challenges of replacing those not considered natural. In the main section on natural hydrocolloids, both those hydrocolloids considered natural because of no chemical processing, and the borderline hydrocolloids (those with simple chemical processing but considered natural by some consumers) are discussed in order to cover the grey areas.