Microsoft Outlook is a personal information manager software system from Microsoft, available as a part of the Microsoft Office suite. Though primarily an email client, Outlook also includes such functions as calendaring, task managing, contact managing, note-taking, journal logging, and web browsing.

Individuals can use Outlook as a stand-alone application; organizations can deploy it as multi-user software (through Microsoft Exchange Server or SharePoint) for such shared functions as mailboxes, calendars, folders, data aggregation (i.e., SharePoint lists), and appointment scheduling. Microsoft has released apps for most mobile platforms, including iOS and Android. In addition, Windows Phone devices can synchronize almost all Outlook data to Outlook Mobile. Using Microsoft Visual Studio, developers can also build their own custom software that works with Outlook and Office components.