Lanthanide-doped　nanocrystals　typically　exhibit　limited　time-gated　nonlinear　luminescence　with　microsecond　lifetimes　because　of　their　parity-forbidden　4f–4f　transitions.　Here　the　direct　observation　of　ultralong-lived　upconversion　luminescence　by　coupling　molecular　triplet　orbitals　to　lanthanide-doped　nanocrystals　is　reported.　Through　careful　manipulation　of　the　molecular　triplet　states,　nanohybrids　capable　of　producing　ultralong　upconversion　lifetimes　up　to　1.37　s　and　tunable　color　output　are　constructed,　surpassing　the　intrinsic　lifetime　of　lanthanide　ions　by　a　factor　of　4500.　In　addition　to　the　exciton　migration　pathway　from　the　4f　levels　of　lanthanide　ions　to　the　molecular　singlet　and　then　to　triplet　states,　direct　activation　of　the　triplet　state　by　exciton　from　the　4f　levels　is　observed.　This　phenomenon　significantly　reduces　the　required　photon　energy　(by　more　than　0.83 eV)　for　stimulation　of　the　triplet　state　compared　to　the　process　involving　intersystem　crossing.　Taking　advantage　of　the　unique　properties　of　these　nanohybrids,　a　pulsed　laser-pumped　encryption　system　with　enhanced　security　is　developed by　embedding　additional　passwords　that　contain　information　about　pulse　frequency　and　width.　This　work　provides　a　new　perspective　on　time-resolved　nonlinear　luminescence　with　an　ultrawide　time　dimension　by　engineering　molecular　triplet　states.　©　2023　Wiley-VCH　GmbH.