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Tunable emission in red phosphors is a challenge for the application of wLED. Herein, we reported a new Eu2+ doped oxide based red K 2 MgSiO 4 :Eu2+ phosphor. Under excitation at 319 nm, the K 2 MgSiO 4 : Eu2+ phosphor exhibits a broad band red emission peaking at 648 nm with FWHM ≈231 nm. The structural and spectral analyses suggest that Eu2+ occupy K1/K3O 6 sites and K2/K4O 8 sites to form two Gaussian fitting emissions at 732 nm and 629 nm, respectively. To achieve tunable emission, reducing the Si content is attempted in K 2 MgSi 1-y O 4 :Eu2+. As the Si content decreases from y = 0 to y = 0.04, the emission spectrum shows a blue shift from 648 nm to 523 nm. Therefore, defect-induced color-tunable phosphors from red to yellow are obtained through reducing Si content in the host. This study aims to provide a new research method to guide the development of Eu2+ doped oxide based red phosphors and design idea to obtain tunable emission of phosphors. Moreover, the defect-induced photoluminescence tuning strategy is universal to most luminescent materials. Toc. A novel broad-band red K 2 MgSiO 4 :Eu2+ phosphor and defect-induced tunable emission from red to yellow. [Display omitted] • A novel K 2 MgSiO 4 :Eu2+ red phosphor with ultra-wide emission (FWHM = 231 nm) is revealed. • The emission color of K 2 MgSiO 4 :Eu2+ changes from red to yellow by generating O vacancy defects. • The defect trap depth of O vacancy is discussed to explain the thermal quenching mechanism. [ABSTRACT FROM AUTHOR]