Precision graphene nanoribbons (GNRs) offer distinctive physicochemical properties that are highly dependent on their geometric topologies, thereby holding great potential for applications in carbon‐based optoelectronics and spintronics. While the edge structure and width control has been a popular strategy for engineering the optoelectronic properties of GNRs, non‐hexagonal‐ring‐containing GNRs remain underexplored due to synthetic challenges, despite offering an equally high potential for tailored properties. Herein, we report the synthesis of a wavy GNR (wGNR) embedding periodic eight‐membered rings into its carbon skeleton, which is achieved by the A2B2‐type Diels‐Alder polymerization between dibenzocyclooctadiyne (6) and dicyclopenta[e,l]pyrene‐5,11‐dione derivative (8), followed by a selective Scholl reaction of the obtained ladder‐type polymer (LTP) precursor. The obtained wGNR, with a length of up to 30 nm, is thoroughly characterized by solid‐state NMR, FT‐IR, Raman, and UV‐Vis spectroscopy with the support of DFT calculations. The non‐planar geometry of wGNR efficiently prevents the inter‐ribbon π‐π aggregation, leading to photoluminescence in solution. Consequently, the wGNR can function as an emissive layer for organic light‐emitting electrochemical cells (OLECs), offering a proof‐of‐concept exploration in implementing luminescent GNRs into optoelectronic devices. The fast‐responding OLECs employing wGNR will pave the way for advancements in OLEC technology and other optoelectronic devices.