Psychosis is a debilitating group of symptoms that affects an individual at the same time and occurs over a period of time. These symptoms often include disturbances in behaviour, the thinking process, thought content, perception, affect, and mood. This chapter with briefly explore what psychosis is and then focus on one of the most debilitating psychotic disorders known to mankind, schizophrenia. Note This chapter is meant to be introductory, and the reader is encouraged to seek further information from comprehensive psychiatric texts. This chapter can also be used as a quick revision chapter for students and clinicians.