valley coupling with the carrier spin, [1][2][3][4] robust exciton and trion emission [5] sensitive to biochemical molecular doping, [6,7] many-body [8,9] and valley [10][11][12][13][14][15][16] physics, and great potential in optoelectronic applications for novel photodetector, [17] electroluminescence light source, [18,19] and lasers. [20] Furthermore, single-photon emitters [21][22][23][24] were found in the transition metal dichalcogenide (TMD) semiconductors, which could serve as a cornerstone for quantum information and communication applications in the visible to near infrared region. [25] Up to date the precise nature of these TMD emitters is still under debate and requires further experimental investigation. Generally, these emitters are attributed to excitons trapped in defectinduced potentials which can be tuned by strain gradient and defect engineering. [26] However, dilute quantum emitters exhibiting narrow photoluminescence (PL) peaks were found in these TMDs and their peak wavelengths were diversely distributed across the broad spectral region. The other candidate for 2D quantum emitter is the twisted TMD heterostructure (i.e., two different TMD monolayers stacked together) with interlayer excitons trapped in periodic MoirĂ© potentials, [27,28] which can be regarded as programmable quantum emitter arrays. [29,30] In recent cryogenic measurements, narrow photoluminescence (PL) peaks due to diverse quantum emitters have been found at random locations of monolayer transition metal dichalcogenides (TMDs), which impedes precise optoelectronic applications. Thus, it is of great importance to truly regulate these localized exciton emissions by deterministic spatial and spectral control. Here, such desired emission is primarily demonstrated in monolayer WS 2 nanodisks. The size-dependent PL studies indicate the clear evolution from the broad defect-band emission to a set of spectrally isolated narrow peaks (linewidth of â sub nm) at 4.2 K, which is associated with the prevailing effect of edge defects with the shrinkage of the disk diameter, providing a narrow emission energy range for bound excitons. When the disk diameter is reduced to 300 nm, more than 80% of emitter peaks are located between 610 and 616 nm, verifying the effective control of emission wavelength of these photon emitters. Furthermore, the strategy is extended to prepare scalable WS 2 nanodisk arrays based on flakes of hundreds of ”m, and size-dependent narrow emissions of WSe 2 nanodisks are testified. This work develops a defect-engineering strategy to generate localized exciton emitters toward the promising TMD-based optoelectronic applications.