The Offline Grid Location Addressing Protocol (OGLAP) is a deterministic, offline-first digital addressing system designed for regions where formal street addresses are absent. An estimated four billion people lack a formal address, a deficit concentrated in Sub-Saharan Africa, South Asia, and Latin America that constrains public-service delivery, emergency response, financial inclusion, and participation in the digital economy. Unlike widely adopted existing digital adressing systems, which encode locations on an abstract global grid disconnected from local governance, OGLAP anchors geocodes within a country's existing administrative and territorial hierarchy. The protocol generates a hierarchical machine-readable code, for example, GN-CON-QYTC-B0B1-2282, that encodes country, region, locality, and a sub-metre micro-location, alongside a derived human-readable address such as "B0B1-2282 Yattaya Fossédè, Conakry, Guinea." OGLAP is country-agnostic in specification and country-specific in deployment, parameterised by three JSON configuration files. All encoding, decoding, and reverse geocoding execute entirely on-device with no network dependency, using a static R-tree spatial index and a documented deterministic collision-resolution scheme that guarantees codes are reproducible across devices, basemaps, languages, and time. The protocol uses a dual local/national grid strategy to ensure complete territorial coverage even where administrative boundary data is sparse. A production reference implementation is being deployed in the Republic of Guinea. This document specifies the protocol architecture, encoding algorithms, and stability guarantees, and discusses current limitations including dependence on administrative-boundary data quality and the absence of formal usability validation. Released under the MIT License with Attribution.