It　has　been　well-established　that　light-matter　interactions,　as　manifested　by　diverse　linear　and　nonlinear　optical　(NLO)　processes,　are　mediated　by　real　and　virtual　particles,　such　as　electrons,　phonons,　and　excitons.　Polarons,　often　regarded　as　electrons　dressed　by　phonons,　are　known　to　contribute　to　exotic　behaviors　of　solids,　from　superconductivity　to　photocatalysis,　while　their　role　in　materials’　NLO　response　remains　largely　unexplored.　Here,　the　NLO　response　mediated　by　polarons　supported　by　a　model　ionic　metal　oxide,　TiO2,　is　examined.　It　is　observed　that　the　formation　of　polaronic　states　within　the　bandgap　results　in　a　dramatic　enhancement　of　NLO　absorption　coefficient　by　over　130　times　for　photon　energies　in　the　sub-bandgap　regions,　characterized　by　a　100 fs　scale　ultrafast　response　that　is　typical　for　thermalized　electrons　in　metals.　The　ultrafast　polaronic　NLO　response　is　then　exploited　for　the　development　of　all-optical　switches　for　ultrafast　pulse　generation　in　near-infrared　(NIR)　fiber　lasers　and　modulation　of　optical　signal　in　the　telecommunication　band　based　on　evanescent　interaction　on　a　planar　waveguide　chip.　These　results　suggest　that　the　polarons　supported　by　dielectric　ionic　oxides　can　fill　the　gaps　left　by　dielectric　and　metallic　materials　and　serve　as　a　novel　platform　for　nonlinear　photonic　applications.　©　2023　Wiley-VCH　GmbH.