Our rst principles calculations demonstrate that FE MOX 2 monolayers have strong in-plane piezoelectric response, which is not only signicantly larger than that of well-known 1H-type 2D piezoelectrics e.g., 1H-MoS 2 but also remarkably stronger than some of the bulk piezoelectrics such as w -AlN or w -GaN. These monolayers also exhibit remarkably large anisotropy in their piezo-response i.e., piezo-response due to strain along a-direction is about an order of magnitude larger than that of along b-direction. We also show that change in magnetic order can change piezo-response in multiferroelectric VOX 2 monolayers, which can potentially couple piezoelectricity and magnetism. We believe that this work will inspire more research in searching for new piezoelectric materials that can couple strongly with magnetism. Also, such large in-plane piezo-response can particularly be benecial for 2D nanoscale exible piezodevices e.g., actuators purely based on in-plane displacement.