Developing　violet‐light‐excitable　deep‐red　(650–660 nm)　Eu2+‐activated　phosphor　is　essential　for　full‐spectrum　lighting.　However,　the　related　phosphors　with　facile　synthesis,　excellent　optical　performance,　and　superior　thermal　stability　are　scarce.　Herein,　a　new　class　of　(Sr,Ba)Lu2O4:　Eu2+　deep‐red　phosphor　(660 nm)　excitable　by　violet　light　via　Ba2+‐induced　local　structure　engineering　is　reported.　Impressively,　tunable　emission　from　615　to　682 nm,　accompanied　by　significant　improvement　of　thermal　stability　(81%@423 K),　is　achieved　by　partially　substituting　Sr2+　by　Ba2+　in　SrLu2O4:　Eu2+.　Crystal　field　analysis,　density　functional　theory　calculations,　and　thermoluminescence　spectra　confirm　that　the　strong　distortion　and　enhanced　covalency　of　[EuO6]　octahedron　are　responsible　for　spectral　tunability,　and　the　formation　of　shallow　trapping　states　is　beneficial　for　electron　compensation　to　inhibit　thermal　quenching　in　the　Sr0.85Ba0.15Lu2O4:　Eu2+　phosphor.　Finally,　a　white　light‐emitting　diode　prototype　fabricated　by　coupling　of　the　Sr0.85Ba0.15Lu2O4:　Eu2+　deep‐red　phosphor　and　commercial　blue/green　phosphors　with　violet　chip　can　yield　sunlight‐like　white　light　with　an　ultra‐high　color　rendering　index　(Ra = 95.2,　R9 = 97.0)　and　an　appropriate　correlated　color　temperature　of　4121 K,　verifying　its　significant　application　potential　in　full‐spectrum　solid‐state　lighting.