How to change branch name in Azure DevOps

Unfortunately, you are not able to rename a branch. However, you can create a new branch from the branch which you want to rename then you can delete that branch.

As per the design, the rename of azure repo branches is not implemented. You can see this existing similar thread

Microsoft's documentation page "Rename old branches" gives the following instructions:

1. open repo > Branches view.
2. locate the old branch.
3. hover over the old branch > ...(More) icon > + New Branch.
4. enter the new branch name > Create branch.
5. hover over the old branch > trash icon (Delete branch).

There is no direct way to rename the branch in azure DevOps but the alternative is to delete the branch and rename it.