The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking and essentially establishes the Internet.

Internet Protocol has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, Internet Protocol defines packet structures that encapsulate the data to deliver. It also defines addressing methods that used to label the datagram with source and destination information.

Historically, IP was the connectionless datagram service in the original Transmission Control Program. It was introduced by Vint Cerf and Bob Kahn in 1974. Therefore the Internet protocol suite often referred to as TCP/IP.
The first major version of is, Internet Protocol Version 4 (IPv4), is the dominant protocol of the Internet. Its successor, Internet Protocol Version 6 IPv6, has been growing in adoption for the last years, reaching almost 20% of the Internet traffic as of April 2018.