Git mergetool generates unwanted .orig files

Question

When I do a merge conflict resolution with Kdiff3 (and other merge tool I tried) I noticed that on resolution a *.orig file is created. Is there a way for it to

Answer 1

To be clear, the correct git command is:

git config --global mergetool.keepBackup false

Both of the other answers have typos in the command line that will cause it to fail or not work correctly.