In the vibrant field of SF5 chemistry, SF5X reagents (X = F, Cl, Br) are at the heart of current investigations in radical pentafluorosulfanylation reactions. Alas! SF5I is the missing link whose existence has not been reported albeit its potential as SF5 donor. We herein report the formal addition of the hitherto unknown SF5I reagent to alkynes by means of a combination of SF5Cl / KI / 18‐crown‐6 ether. The exclusive regio‐ and stereoselective synthesis of unprecedented (E)‐1‐iodo‐2‐(pentafluoro‐l6‐sulfanyl) alkenes was achieved. A consensus was reached through computational and mechanistic studies for the realistic formation of SF5– anion but not SF5I in solution and the rational involvement of SF5· and iodine radicals in the iodo pentafluorosulfanylation reaction.