IBM Notes (formerly Lotus Notes) and IBM Domino (formerly Lotus Domino) are the client and server, respectively, of a collaborative client-server software platform sold by IBM.

IBM Notes provides business collaboration functions, such as email, calendars, to-do lists, contacts management, teamrooms, discussion forums, file sharing, microblogging, instant messaging, blogs, and user directories. IBM Notes can also be used with other IBM Domino applications and databases. IBM Notes 9 Social Edition removed integration with the office software package IBM Lotus Symphony, which had been integrated with the IBM Lotus Notes client in versions 8.x.