Abstract: A new and distinct cultivar of nectarine tree is provided that is named Scarlet Sun. The new cultivar originated from an open-pollinated peach seed of unknown parentage that was planted by the originator when seeking to develop new peach and nectarine cultivars of commercial potential primarily for California growing conditions. The new variety produces large freestone fruit with a high degree of bright red skin coloration. The harvest time is relatively early and commonly provides a crop suitable for commercial harvest from about June 15th to 25th when grown in central San Joaquin Valley of California near Fresno. The new cultivar offers improvements in fruit quality, color, and size over other freestone nectarine cultivars maturing at approximately the same time.