Abstract—This paper investigates the speed limit of information propagation in large wireless networks, which provides fundamental understanding of the fastest information transportation and delivery that a wireless network is able to accommodate. We show that there is a unified speed upper bound for broadcast and unicast communications in large wireless networks. When network connectivity and successful packet delivery are considered, this speed upper bound is a function of node density. As this bound is unreachable with finite node density, we also quantify the gap between the actually achieved speed and the desired upper bound, which converges to zero exponentially as the node density increases to infinity.