Optimizing the route of oil transmission pipelines is one of the most critical phases in the development of energy infrastructure and in reducing the economic and environmental risks of large-scale transmission projects. Given the pivotal role of spatial data and advanced geospatial analysis tools in infrastructure decision-making, the present study focuses on the design and routing of an oil pipeline between the petrochemical facilities of Mamasani and Gachsaran using Geographic Information Systems (GIS). Two main approaches were employed in this research. First, a Digital Elevation Model (DEM) of the region was used to generate a slope map, and a preliminary route was designed through Cost Distance analysis. Next, the land use map of the study area was converted into raster data, and a second route was proposed based on spatial prioritization of land types including agricultural lands, forests, residential areas, wetlands, and salt marshes. A comparison between the two designed routes revealed that the land use-based route, with an approximate length of 89.6 kilometers, was shorter than the slope-based route (95.4 kilometers) and also avoided high-risk and sensitive areas such as urban zones and heavily utilized lands. This route is also more cost-effective in terms of construction and implementation. Furthermore, the use of classified land use data in the routing process significantly enhanced accuracy and reduced errors in final path selection. By leveraging GIS analytical capabilities and integrating various spatial layers, this study offers a reliable model for pipeline routing in areas with complex topographic conditions. The findings of this research can inform similar energy transmission projects and contribute to sustainable infrastructure development across other regions of the country.