While developing Islamic economics as a discipline, it is necessary to define the nature, scope and subject-matter in order to clarify the object of study and indicate the boundaries of its reach. Islamic economists in this regards have put effort to define Islamic economics to inform readers about its underlying norms and aspirations as well as the objectives it intends to serve. This paper attempts to observe Islamic economists’ approaches in defining Islamic economics. Classification of various definitions proposed by Islamic economists will also be discussed. By this observation we will be able to see the different points of view among the scholars in conceiving Islamic economics’ subject matter, as well as see the shades of thought in determining Islamic economics’ object of study and the level of development of Islamic economics as a body of knowledge.