Google Research has released MilleMiglia, an open-source C++ instance generator designed to create realistic benchmarks for middle-mile logistics optimization. The tool addresses a significant gap in operational research: while first-mile and last-mile logistics have been extensively studied and modeled as vehicle routing problems, the middle mile—the critical regional and continental distribution network that moves the bulk of goods between distribution centers—has received limited academic attention, largely because logistics companies treat their network data as proprietary. MilleMiglia bridges this gap by generating privacy-preserving, realistic benchmarks that capture the unique constraints of middle-mile operations, including time windows for connections between distribution centers and the relay nature of shipments across multiple vehicles and handling cycles. The tool enables researchers to develop optimization algorithms without access to sensitive company data, potentially leading to more efficient global supply chains. The open-source release, developed by Google engineers Aymane Lotfi and Thibaut Cuvelier, makes code and documentation available on GitHub to establish a foundation for future research in this commercially significant domain.