Guanyin occupies a prominent place in East Asian Religions, being honoured in both Buddhist and Taoist temples. This figure, often referred to as the Goddess of Mercy, is frequently depicted as a young barefoot maiden with long dark hair and flowing white robes. Surprisingly, however, this maiden started her career as a masculine bodhisattva. In addition many multi-armed and multi-headed forms of Guanyin can be found in different temples and a profusion of different attributes have appeared over time. This thesis looks at the degree to which other religious figures and cultural values have contributed to the development of the iconography of Guanyin. In studying and comparing the various iconographic forms in the diverse parts of East Asia we can see how local beliefs and other religious figures have shaped Guanyin's imagery. We can also see that it is the malleability of this cult figure that makes this possible. It is for this reason that the cult of Guanyin has been so successful. Part of the investigation into the influences that shaped Guanyin's imagery will involve a discussion of the 'sex change'. This has been the subject of much debate. Several figures can be said to have influenced this feminine form, these include Hārītī, Shengmu and Tārā. What is remarkable about the cult of Guanyin and explains its success, is that because imagery changes according to the needs of devotees, so gender also changes. This malleable quality of Guanyin is not restricted to gender but extends to other features and functions of Guanyin. These are determined by the beliefs of the various communities to which the cult has spread and evidenced by the interplay with the cults of other deities such as that of the Taoist goddess Mazu. In this particular case we can see first hand an example of the assimilation process at work. This thesis is the result of much 'on site' research, all photographs being my own except where cited otherwise. I use the 'Pinyin' system of transliteration except where the Wade-Giles form is more commonly known, which I show in square brackets.