[en] This work investigates the promising multi-modal luminescence (upconversion (UC), downshifting (DS) and quantum cutting (QC)) properties of RE"3"+ (Tm"3"+, Yb"3"+) and Bi"3"+ activated GdNbO_4 phosphors synthesized using the well-known solid state reaction method. Structural characterization using x-ray diffraction measurements confirms the formation of the pure phase of the GdNbO_4 host with no impurities. The optical band gap (E _g) of GdNbO_4 (with and without RE"3"+ ions) calculated from UV–Vis–near-infrared (NIR) measurements was found to be the same ∼4.44 eV which indicates that GdNbO_4 is a wide band gap material. Further, Bi"3"+ doping presents an interesting E _g tuning of the GdNbO_4 phosphor, i.e. E _g increases up to 5.38 eV. In terms of luminescence, this material produces intense blue and NIR emission via multi-modal optical processes. On NIR excitation (λ _e_x_c  =  980 nm), Gd_0_._9_4Tm_0_._0_1Yb_0_._0_5NbO_4 produces intense upconverted blue and NIR and relatively weak red emission. In addition to the UC process, Gd_0_._9_4Tm_0_._0_1Yb_0_._0_5NbO_4 also exhibits pump power dependent variation in fluorescence intensity ratio for I _4_7_2/I _4_7_7 showing the applicability of this material as an optical heater. On UV excitation (λ _e_x_c  =  265 nm), Gd_0_._9_9Tm_0_._0_1NbO_4 produces intense DS blue emission due to the Tm"3"+ ion, overlapped with the emission of the (NbO_4)"3"− ion through strong energy transfer (ET) from (NbO_4)"3"− to Tm"3"+ ions. Interestingly, NIR QC has also been successfully observed in Gd_0_._9Yb_0_._1NbO_4, Gd_0_._8_9Bi_0_._0_1Yb_0_._1NbO_4 and Gd_0_._7_9Tm_0_._0_1Yb_0_._2NbO_4 phosphors through cooperative ET from the (NbO_4)"3"− group to the Yb"3"+ ion, Bi(6s)–Nb(4d) to the Yb"3"+ ion and the Tm"3"+ ion to the Yb"3"+ ion, respectively. The mechanisms involved in these processes are explained in detail in this work. The QC efficiency in this work has been found to be ∼177%. Thus, the multi-modal luminescence (UC, DS and QC) property of this material makes it a promising candidate for display devices, spectral converters for enhancing the efficiency of silicon solar cells, etc. (paper)