OpenFabrics Interfaces (OFI) is a new family of application program interfaces that exposes communication services to middleware and applications. Libfabric is the first member of OFI and was designed under the auspices of the OpenFabrics Alliance by a broad coalition of industry, academic, and national labs partners over the past two years. Building and expanding on the goals and objectives of the verbs interface, libfabric is specifically designed to meet the performance and scalability requirements of high performance applications such as Message Passing Interface (MPI) libraries, Symmetric Hierarchical Memory Access (SHMEM) libraries, Partitioned Global Address Space (PGAS) programming models, Database Management Systems (DBMS), and enterprise applications running in a tightly coupled network environment. A key aspect of libfabric is that it is designed to be independent of the underlying network protocols as well as the implementation of the networking devices. This paper provides a brief discussion of the motivation for creating a new API, describes the novel requirements gathering process which drove its design, and summarizes the API's high-level architecture and design.