Bliss, originally titled Bucolic Green Hills, is the default wallpaper of Microsoft's Windows XP operating system. It is a photograph of green rolling hills and daytime sky with cirrus clouds. Charles O'Rear, a former National Geographic photographer, took the photo in January 1996 near the Napa–Sonoma county line, California, after a phylloxera infestation forced vineyards to be cleared from the hill years prior. He used the Mamiya RZ67 camera and Fujifilm's Velvia film to create the photograph; O'Rear remarked that he did not enhance or manipulate the photograph.

Initially a stock photo available through his photo agency Westlight that was acquired by Bill Gates' Corbis in 1998, Microsoft obtained full rights of the photograph in 2000 and then used it to promote Windows XP. Bliss received positive reception from reviewers and has been speculated to be the most viewed photograph in history by Microsoft and journalists. Microsoft has reused the photograph in several promotions since the release of Windows XP. Photographers have attempted to re-create the iconic image, but the rolling hill has since become a vineyard again.