This document provides an introduction to Ubuntu, an open-source Linux operating system. It discusses what Ubuntu is, why users would want to use it, its default applications, and recent Ubuntu releases. It then provides overviews of the Ubuntu desktop, panels, menus, icons, virtual desktops, and the Nautilus file browser. It discusses how files are handled in Ubuntu and basic day-to-day file management tasks. The document concludes with exercises for the reader to complete.