A Microsoft account or MSA (previously known as Microsoft Passport, .NET Passport, and Windows Live ID) is a single sign-on personal user account for Microsoft customers to log in to consumer Microsoft services (like Outlook.com), devices running on one of Microsoft's current operating systems (e.g. Microsoft Windows computers and tablets, Xbox consoles), and Microsoft application software (e.g. Microsoft Office, Microsoft Teams).

Microsoft account allows users to sign into websites that support this service using a single set of credentials - these usernames are in the same form as an email address. Microsoft account offers a user two different methods for creating an account:

Both methods don't require, as of 2025, mobile verification. The domains @live.com and @passport.com, as well as other domains are no longer offered, but existing accounts are maintained.

Microsoft websites, services, and apps such as Bing, MSN and Xbox Live use Microsoft account as a means of identifying users. There are also several other companies that use it, such as the Hoyts website which is hosted by NineMSN.

Windows XP and later has an option to link a local Windows user account with a Microsoft account, thus automatically logging users in to their Microsoft account whenever a service is accessed. Starting with Windows 8 and Windows Server 2012, Windows allows users to directly authenticate into their PCs using their Microsoft account rather than a local or domain user.

In addition to using an account password, users can login to their Microsoft account by accepting a mobile notification sent to a mobile device with Microsoft Authenticator, a FIDO2 security token or by using Windows Hello. Users can also set up two-factor authentication by getting a time-based, single-use code by text, phone call or using an authenticator app.

Users' credentials are not checked by Microsoft account-enabled websites, but by a Microsoft account authentication server. A new user signing into a Microsoft account-enabled website is first redirected to the nearest authentication server, which asks for username and password over an SSL connection. The user may select to have their computer remember their login: a newly signed-in user has an encrypted time-limited cookie stored on their computer and receives a triple DES encrypted ID-tag that previously has been agreed upon between the authentication server and the Microsoft account-enabled website. This ID-tag is then sent to the website, upon which the website plants another encrypted HTTP cookie in the user's computer, also time-limited. As long as these cookies are valid, the user is not required to supply a username and password. If the user actively logs out of their Microsoft account, these cookies will be removed.

Microsoft also offer a work or school account which are set up by an administrator as part of an organization. These accounts are separate from Microsoft accounts (which is also called personal account) and cannot be merged, but may be used side-by-side by a user. A work or school account uses the Azure Active Directory domain platform.