Understanding　the　onset　of　plasticity　in　SrTiO3　(STO)　is　critical　for　enhancing　its　mechanical　performance　and　reliability　in　functional　applications.　Despite　known　influences　of　doping　and　loading　conditions,　their　combined　effects　on　dislocation　nucleation　in　STO　remain　underexplored.　In　this　study,　we　investigate　the　incipient　plasticity　of　(001)-oriented　STO　single　crystals　by　systematically　varying　displacement　rates　and　incorporating　Nb　doping,　using　displacement-controlled　nanoindentation　and　first-principles　calculations.　We　reveal　a　non-monotonic　dependence　of　the　critical　shear　stress　on　displacement　rate,　governed　by　the　interplay　between　stress　relaxation　and　thermal　activation　time.　Nb　doping　is　shown　to　reduce　the　critical　stress　for　dislocation　nucleation　by　lowering　the　stacking　fault　energy　along　the　direction　and　altering　the　local　charge　environment,　as　evidenced　by　density　functional　theory　(DFT)　and　Bader　charge　analysis.　These　insights　advance　the　understanding　of　deformation　mechanisms　in　functional　ceramics　and　offer　practical　guidance　for　tailoring　their　mechanical　responses　through　defect　and　doping　engineering.　©　2025　Elsevier　Ltd