1. M-x magit-show-refs : This shows the list of local as well as remote branches.
  2. Go to the Branches section (One at the top, most likely you are already there.)
  3. Navigate via up/down arrows and select the branch to delete by typing x (for magit-delete-thing) followed by RET
  4. In the lower section (mini-buffer) you'll see the list of branches.
  5. For unmerged branches you get a confirmation prompt. Type y to confirm.

If you liked this micro-TIL, checkout my other notes at my Dendron Site