Wireless sensor networks (WSNs) are taking a major share with almost all types of different applications and especially, it is most suited in very harsh and tough environments, where it is too hard to deploy conventional network applications, for example in the forest fire area, battlefields during the war, chemical and thermal sites, and also for few underwater applications. WSNs are now becoming part of almost all applications because of their ease in deployment and cheaper cost. These networks are resource constraints, very small in size, computation, and with much less communication capabilities. Nodes are normally deployed in random fashion, and it's too hard to find their location because there is no any predefined way like conventional networks to discern location. Location is highly important to know the data correlation: for example its target tracking, and to know actual vicinity of the any event occurrence. This chapter describes the current available approaches, issues, and challenges with current approaches and future directions for node localization, one by one. Node localization is highly important for large sensor networks where users desire to know about the exact location of the nodes to know the data location. © 2012, IGI Global.