With the advances in wireless technologies and development of mobile devices, Mobile Ad hoc Networks have emerged as the milestone and play an important role in establishing communication using no fixed infrastructure. Nodes are free to move randomly and communicate with each other through single hop if within transmission range or through multiple hop beyond transmission range. Due to unpredictable behavior of such networks, it is difficult to maintain the required Quality of Service (QoS). QoS in MANETs refers to the provision of guaranteed services on the network layer, defined in the performance metrics between application and service provider. The first important task in QoS network routing is to find a feasible route through the network between source and destination. This route should satisfy all the requirements to fulfill the QoS constraints for the desired service. The focus of the book throughout has been on the study and development of QoS constrained routing protocols to ensure better QoS provisioning.