Happy Isles is a group of small isles in the Merced River in Yosemite National Park, California, United States. They are located at the easternmost end of the Yosemite Valley floor. This scenic spot is the starting point for the Mist Trail, and is also the northern trailhead for the John Muir Trail. Happy Isles is also the trailhead for popular hiking destinations along the Mist Trail and Half Dome.