The　intriguing　optical　response　associated　with　the　vanishingly　small　dielectric　primitivity　in　epsilon-near-zero　(ENZ)　materials　has　offered　unprecedented　opportunities　for　photonics.　Due　to　the　high-limit　of　doping　concentration,　current　homogeneous　ENZ　materials　based　on　heavily　doped　conductive　oxide　including　ITO　usually　exhibit　a　zero-permittivity　wavelength　(λ0)　longer　than　1200　nm.　Here,　this　is　identified　with　combined　theoretical　and　experimental　investigations　that　stoichiometric　rutile-type　RuO2　(r-RuO2)　exhibits　the　shortest　λ0　of　near　800　nm　among　conductive　oxides,　benefiting　from　the　high　free　electron　concentration　with　characteristic　Drude-type　response.　The　ENZ　effect　is　manifested　by　the　strong　field　enhancement　and　the　large　nonlinear　optical　(NLO)　response　in　colloidal　processed　r-RuO2　nanoparticles　(NPs)　and　thin　films.　By　ultrafast　transient　spectroscopy,　the　strong　NLO　response　in　r-RuO2　NPs　is　revealed　to　be　the　result　of　rapid　thermalization/cooling　of　free　electrons　in　the　strong　hybridized　Ru-4d/O-2p　orbitals.　The　ultrafast　optical　nonlinearity　is　exploited　further　for　the　development　of　multi-purpose　all-optical　switches　that　enable　stable　pulse　laser　generation　in　four　mode-locked　and　Q-switched　fiber　lasers.　Our　results　underscore　the　potential　of　stoichiometric　metallic　metal　oxides　as　alternative　ENZ　materials　for　nonlinear　photonics　applications　in　the　visible　and　NIR　regions.　©　2025　Wiley-VCH　GmbH.