User Groups are enabled for all Slack teams on paid plans (both Standard and Plus). New groups can be created in the Team Directory panel in your desktop app. You can give each a descriptive name and add a note on purpose to help others understand what each group is for. The team directory will then list your team’s existing user groups and show the details of each, along with the the group’s members.
使用者可以被分類成 Group，然後可以針對某一個 Group 傳訊息。而 Plus Plan 的用戶可以透過 SSO 機制將群組資訊帶進來用：
For teams using Single Sign On (SSO) on the Plus plan, you can even use groups to control provisioning accounts from your SSO tools. Users of Active Directory in OneLogin, PingOne, PingFederate, or Okta can take advantage of this built-in user provisioning support to add employees automatically into Slack User Groups matching each employee’s existing group rights, roles and permissions in your internal directory.
另外也有提供 API 讓你用，所以 Standard Plan 用戶也可以自己寫，然後塞進去。