The significance of the HTTP protocol in web services lies in its role as the foundation of data communication on the World Wide Web. Hypertext Transfer Protocol (HTTP) facilitates the transfer of hypertext between a client (typically a web browser) and a server, enabling the retrieval of web pages and other resources. Its simplicity and extensibility have made it a standard for web communication. The protocol also supports various features like URL request methods, security via HTTPS, and session management, which are crucial for building interactive and secure web applications.