Delete a local branch feature:

git branch -d feature

This will fail if the branch is not merged. To delete the branch regardless:

git branch -D feature

To delete a remote branch feature on remote origin (warning: There is no confirmation!):

git push origin :feature

Note: git-branch documentation lists documentation for the option -r which works on remote tracking branches, not branches on the remote; git branch -D -r origin/feature will delete the remote tracking branch origin/feature, not the branch feature on remote origin. Pulling/fetching from the remote again will recreate that tracking branch.

To delete remote tracking branches that no longer exist on the remote:

git fetch --prune