Eyes are said to be the windows of body, by which this beautiful world is visualized. Human eye has a unique structure and is vulnerable to numerous infections. Whenever anatomical structures are breached, host defenses come into play, but if infection is severe and not treated timely, it could lead to visual impairment or blindness. Parasitic infections are considered, the significant causes of ophthalmic diseases worldwide. In this chapter, an overview of ocular parasitic infections (OPI) is detailed out, with an initial brief introduction followed by description of anatomy of the human eye and various defense mechanisms to provide better understanding of the parasitic infections affecting different parts of human eye. The last part includes individual details of various human ocular parasitic infections. Ocular infections can be classified based on either the etiological agent or according to the anatomical site of infection. The parasitic etiological agents include mainly protozoa, helminths and ectoparasites. Due to the complex life cycles of parasites and their tendency to cause wide range of pathologic lesions, different parasites/parasitic infections have been addressed separately, including brief epidemiology, clinical features, diagnosis and treatment.