This disclosure describes systems, methods, and devices related to multi-user uplink channel sounding. A device may determine a channel sounding sequence with one or more access points (APs), wherein the channel sounding sequence comprises a null data packet announcement (NDPA) communicated with at least one of the one or more APs. The device may determine a first group of station devices (STAs) associated with a first basic service set (BSS). The device may cause to send a trigger frame to the first group of STAs to solicit an uplink NDP from each STA of the first group of STAs. The device may identify a first uplink NDP received from a first STA of the first group of STAs. The device may identify a second uplink NDP received from a second STA of a second group of STAs.