Mobile ad-hoc networks (MANETs) are wireless networks formed without any preexisting infrastructure. Nodes in a MANET are mobile and communicate in a multi-hop fashion through wireless connections. Routing is challenging in MANETs due to their dynamic topology. There are several routing protocols for MANETs including proactive, reactive, and hybrid protocols. Common protocols discussed are AODV, DSDV, and DSR. Simulation tools like NS-2 are often used to study and compare MANET routing protocols. MANETs have applications in areas like disaster recovery, mesh networks, opportunistic networking, and vehicular networks.