Acceleration of singlet‐triplet intersystem crossings (ISC) is instrumental in bolstering triplet exciton harvesting of multi‐resonance thermally activated delayed fluorescent (MR‐TADF) emitters. This work describes a simple gold(I) coordination strategy to enhance the spin‐orbit coupling of green and blue BN(O)‐based MR‐TADF emitters, which results in a notable increase in rate constants of the spectroscopically observed ISC process to 3×109 s−1 with nearly unitary ISC quantum yields. Accordingly, the resultant thermally‐stable AuI emitters attained large values of delayed fluorescence radiative rate constant up to 1.3×105/1.7×105 s−1 in THF/PMMA film while preserving narrowband emissions (FWHM=30–37 nm) and high emission quantum yields (ca. 0.9). The vapor‐deposited ultrapure‐green OLEDs fabricated with these AuI emitters delivered high luminance of up to 2.53×105 cd m−2 as well as external quantum efficiencies of up to 30.3 % with roll‐offs as low as 0.8 % and long device lifetimes (LT60) of 1210 h at 1000 cd m−2. A simple gold(I) coordination strategy affords highly efficient narrowband green and blue multi‐resonance thermally activated delayed fluorescence with emission quantum yields of ca. 0.9 and considerably shortened lifetimes down to 5.5 μs. The resultant AuI emitters deliver ultrapure‐green OLEDs with external quantum efficiencies of up to 30.3 %, alongside diminished roll‐offs as low as 0.8 % and device lifetimes (LT60) of 1210 h at 1000 cd m−2.