AbstractConventional bulk and thin piezoelectric materials based film bulk acoustic resonators (FBARs) are facing an insurmountable challenge for millimetric frequency applications due to the poor piezoelectric properties of the materials when their thickness reaches the sub‐micron regime. Novel FBARs for ultra‐high working frequencies are in urgent demand to meet the requirements of the fast‐growing 5/6G telecommunication techniques. Recent advances in 2D piezoelectric nanomaterials create an opportunity in this perspective. Here, the first FBAR chip based on 2D 3R‐MoS₂ ultrathin piezoelectric flakes with a solidly mounted resonator (SMR) architecture is reported. The typical resonant frequency for an SMR device based on ≈200 nm 3R‐MoS₂ flake reaches over 25 GHz with high reproducibility. Theoretical and finite element analysis suggest that the observed resonance is of longitudinal acoustic modes. This study demonstrates for the first time that the access to 2D piezoelectric nanomaterials makes high performance piezoelectric devices feasible for various promising applications including high‐speed telecommunication, acousto‐optic, and sensor fields,etc.