Multi-user null data packet (MU-NDP) sounding within multiple user, multiple access, and/or MIMO wireless communications. Within communication systems including multiple wireless communication devices (e.g., one or more APs, STAs, etc.), channel sounding of the selected communication links between the various wireless communication devices is performed. A MU-NDP announcement frame is transmitted to and received by various wireless communication devices indicating which of those wireless communication devices (e.g., one, some, or all) are being sounded. Then, respective NDP sounding frames are transmitted via the communication links corresponding to those wireless communication devices (e.g., one, some, or all) are being sounded, and sounding feedback signals are subsequently sent back to the original transmitting wireless communication device. In some instances, after transmission of the MU-NDP announcement frame, a clear to send (CTS) is sent from at least one of the wireless communication devices thereby precipitating the transmission of the NDP sounding frames.