Enterprise application integration (EAI) is a business term for the plans, methods, and tools aimed at modernizing, consolidating, and coordinating the computer applications in a business. Typically, a business has existing legacy applications and data and wants to continue to use them while adding or migrating to a new set of applications and systems that exploit the Internet, e-Commerce, Extranet, Intranet, and other new technologies.

This may require a totally new view of how a business operates, seeing how existing applications fit into the new view, and then devising ways to efficiently reuse what already exists while adding new applications and data. This can encompass methodologies such as object-oriented programming, distributed, cross-platform communications, the modification of business resource planning to fit the new objectives, and other approaches.