It is recommended that you make a backup in case you wish to use your data in the future. See the Backups page for details.
To uninstall MantisBT:
Delete the MantisBT directory and all files and subdirectories.
Drop all MantisBT tables from the database, these can be identified by the configured prefix for the installation. The default prefix is 'mantis'.
Remove any customizations or additions that you may have made.