Text. The C3‐alkenylation of indoles have been developed by means of a novel in situ iodination tactic which is capable of mediating the Heck coupling with alkenes. The method features specific site‐selectivity oriented by the C‐I bond, high‐step efficiency without pre‐functionalization for C‐halogen bond construction, as well as the highly general tolerance to different terminal alkenes, including unactivated alkenes, acrylates, acrylic acid, vinyl sulfone as well as different vinyl functionalized natural products.