Bliss, originally titled Bucolic Green Hills, is the default wallpaper of Microsoft's Windows XP operating system. It is an unedited photograph of a green hill and blue sky with white clouds in the Los Carneros American Viticultural Area of Wine Country, California. Charles O'Rear took the photo in January 1996 and Microsoft bought the rights in 2000. It is estimated that billions of people have seen the picture, possibly making it the most viewed photograph in history.

A wallpaper or background is a digital image used as a decorative background of a graphical user interface on the screen of a computer, smartphone or other electronic device. On a computer, wallpapers are generally used on the desktop, while on a mobile phone they serve as the background for the home screen. Though most devices include a default background image, modern devices usually allow users to manually change the background image.