The Protocol Wars were a long-running debate in computer science that occurred from the 1970s to the 1990s, when engineers, organizations and nations became polarized over the issue of which communication protocol would result in the best and most robust networks. This culminated in the Internet–OSI Standards War in the 1980s and early 1990s, which was ultimately "won" by the Internet protocol suite (TCP/IP) by the mid-1990s when it became the dominant protocol suite through rapid adoption of the Internet.

In the late 1960s and early 1970s, the pioneers of packet switching technology built computer networks providing data communication, that is the ability to transfer data between points or nodes. As more of these networks emerged in the mid to late 1970s, the debate about communication protocols became a "battle for access standards". An international collaboration between several national postal, telegraph and telephone (PTT) providers and commercial operators led to the X.25 standard in 1976, which was adopted on public data networks providing global coverage. Separately, proprietary data communication protocols emerged, most notably IBM's Systems Network Architecture in 1974 and Digital Equipment Corporation's DECnet in 1975.

The United States Department of Defense (DoD) developed TCP/IP during the 1970s in collaboration with universities and researchers in the US, UK, and France. Internet Protocol version 4 (IPv4) was released in 1981 and was made the standard for all DoD computer networking. By 1984, the international reference model OSI model, which was not compatible with TCP/IP, had been agreed upon. Many European governments (particularly France, West Germany, and the UK) and the United States Department of Commerce mandated compliance with the OSI model, while the US Department of Defense planned to transition from TCP/IP to OSI.

Meanwhile, the development of a complete Internet protocol suite by 1989, and partnerships with the telecommunication and computer industry to incorporate TCP/IP software into various operating systems, laid the foundation for the widespread adoption of TCP/IP as a comprehensive protocol suite. While OSI developed its networking standards in the late 1980s, TCP/IP came into widespread use on multi-vendor networks for internetworking and as the core component of the emerging Internet.

Computer science was an emerging discipline in the late 1950s that began to consider time-sharing between computer users and, later, the possibility of achieving this over wide area networks. In the early 1960s, J. C. R. Licklider proposed the idea of a universal computer network while working at Bolt Beranek & Newman (BBN) and, later, leading the Information Processing Techniques Office (IPTO) at the Advanced Research Projects Agency (ARPA, later, DARPA) of the US Department of Defense (DoD). Independently, Paul Baran at RAND in the US and Donald Davies at the National Physical Laboratory (NPL) in the UK invented new approaches to the design of computer networks.

Baran published a series of papers between 1960 and 1964 about dividing information into "message blocks" and dynamically routing them over distributed networks. Davies conceived of and named the concept of packet switching using high-speed interface computers for data communication in 1965–1966. He proposed a national commercial data network in the UK, and designed the local-area NPL network to demonstrate and research his ideas. The first use of the term protocol in a modern data-communication context occurs in an April 1967 memorandum A Protocol for Use in the NPL Data Communications Network written by two members of Davies' team, Roger Scantlebury and Keith Bartlett.

Licklider, Baran, and Davies all found it hard to convince incumbent telephone companies of the merits of their ideas. AT&T held a monopoly on communication infrastructure in the United States, as did the General Post Office (GPO) in the United Kingdom, which was the national postal, telegraph and telephone service (PTT). They both believed speech traffic would continue to dominate and continued to invest in traditional telegraphic techniques. Telephone companies were operating on the basis of circuit switching, alternatives to which are message switching or packet switching.

Bob Taylor became the director of the IPTO in 1966 and set out to achieve Licklider's vision to enable resource sharing between remote computers. Taylor hired Larry Roberts to manage the programme. Roberts brought Leonard Kleinrock into the project; Kleinrock had applied mathematical methods to study communication networks in his doctoral thesis. At the October 1967 Symposium on Operating Systems Principles, Roberts presented the early "ARPA Net" proposal, based on Wesley Clark's idea for a message switching network using Interface Message Processors (IMPs). Roger Scantlebury presented Davies' work on a digital communication network and referenced the work of Paul Baran. At this seminal meeting, the NPL paper articulated how the data communication for such a resource-sharing network could be implemented.