New-UnifiedGroup: In order to create a group, you must specify an owner.

Maybe you tried to create a new O365 group using the New-UnifiedGroup cmdlet and hit upon this error?

Sure, it sounds like an Owner is required but there are many examples of this cmdlet being run without an Owner. For example this post.

I didn’t find much while Googling on this until I came across this Tony Redmond post that tangentially gave the answer:

If you don’t pass a value in Owner, Exchange Online sets the signed in user as a group owner along with the people specified in ManagedBy.

I was running the New-UnifiedGroup cmdlet while logged in to Exchange Online via an App Registration. That’s why I was getting this error, while anyone running this under an admin account will not get the error as they will silently be made the owner of the new group. Hah!

Update: Good to know, if using Graph API. From:

Creating a group using the Group.Create application permission without specifying owners will create the group anonymously and the group will not be modifiable. You can use the POST operation and add owners to the group while creating it to specify owners who can modify the group.

Creating a Microsoft 365 group programmatically with an app-only context and without specifying owners will create the group anonymously. Doing so can result in the associated SharePoint Online site not being created automatically until further manual action is taken.