A mobile ad hoc network (MANET) consists of mobile wireless nodes. The communication between these mobile nodes is carried out without any centralized control. MANET is a self organized and self configurable network where the mobile nodes move arbitrarily. The mobile nodes can receive and forward packets as a router. Routing is a critical issue in MANET and hence the focus of this thesis along with the performance analysis of routing protocols. We compared three routing protocols i.e. AODV, DSR and OLSR. Our simulation tool will be OPNET modeler. The performance of these routing protocols is analyzed by three metrics: delay, network load and throughput. All the three routing protocols are explained in a deep way with metrics. The comparison analysis will be carrying out about these protocols and in the last the conclusion will be presented, that which routing protocol is the best one for mobile ad hoc networks.