Abstract The development of ultracompact spectrometers is critically important for applications with stringent size and weight constraints, including implantable medical devices, portable electronics, and field‐deployable characterization systems. A monolithic spectrometer based on strain‐engineered monolayer MoS 2 that achieves broadband visible operation (470–750 nm) with 9 nm resolution through a novel strain‐mediated spectral decoding mechanism, is presented. Leveraging the exceptional electromechanical coupling and strain‐tunable optoelectronic properties of 2D MoS 2 , the device utilizes resonant‐frequency electromechanical excitation (20.02–20.08 MHz) to systematically control the spectral response, enabling sub‐10‐nm resolution (Δλ = 9 nm) without conventional dispersive optics. A computationally efficient reconstruction algorithm incorporating Tikhonov regularization with generalized cross‐validation solves the ill‐posed inverse problem while maintaining spectral fidelity (>90% correlation with commercial systems). The 6.5 Å‐thick active layer enables unprecedented miniaturization (50 × size reduction vs conventional systems) while preserving exceptional performance (Q >800, response time <100 µs). This architecture not only establishes a new paradigm for on‐chip spectroscopic systems but also demonstrates immediate applications in hyperspectral imaging (100 µm spatial resolution), CIE‐standard color reconstruction (ΔE <3), and spectrally encrypted communications. By bridging atomic‐scale strain engineering and macroscopic spectroscopy, this work provides an avenue for lab‐on‐a‐chip diagnostic platforms, wearable biosensors, and integrated photonic systems.