Following recent advances in the performance of ad hoc networks, the limited life of batteries in mobile devices poses a bottleneck in their development. Consequently, how to minimize power consumption in the Medium Access Control (MAC) layer of ad hoc networks is an essential issue. The power-saving mode (PSM) of IEEE 802.11 involves the Timing Synchronization Function to reduce power consumption for single-hop mobile ad hoc networks (MANETs). However, the IEEE 802.11 PSM is known to result in unnecessary energy consumption as well as the problems of overheating and back-off time delay. Hence, this study presents an efficient power-saving MAC protocol, called p-MANET, based on a Multi-hop Time Synchronization Protocol, which involves a hibernation mechanism, a beacon inhibition mechanism, and a low-latency next-hop selection mechanism for general-purpose multi-hop MANETs. The main purposes of the p-MANET protocol are to reduce significantly the power consumption and the transmission latency. In the hibernation mechanism, each p-MANET node needs only to wake up during one out of every N beacon interval, where N is the number of beacon intervals in a cycle. Thus, efficient power consumption is achieved. Furthermore, a beacon inhibition mechanism is proposed to prevent the beacon storm problem that is caused by synchronization and neighbor discovery messages. Finally, the low-latency next-hop selection mechanism is designed to yield low transmission latency. Each p-MANET node is aware of the active beacon intervals of its neighbors by using a hash function, such that it can easily forward packets to a neighbor in active mode or with the least remaining time to wake up. As a consequence, upper-layer routing protocols can cooperate with p-MANET to select the next-hop neighbor with the best forwarding delay. To verify the proposed design and demonstrate the favorable performance of the proposed p-MANET, we present the theoretical analysis related to p-MANET and also perform experimental simulations. The numerical results show that p-MANET reduces power consumption and routing latency and performs well in extending lifetime with a small neighbor discovery time.