"Hapi Hapi Sunday!"(はぴ☆はぴ サンデー！,Hapi Hapi Sandē!) is the sixth solo single J-pop singer Koharu Kusumi, under the name of "Kirari Tsukishima starring Koharu Kusumi (Morning Musume)" (月島きらり starring 久住小春(モーニング娘。)). It was released on February 4, 2009 in limited edition and regular edition CDs. "Hapi Hapi Sunday!" was created for the anime series Kirarin Revolution—a show in which the main character Kirari Tsukishima is voiced by Koharu Kusumi—for use as its eighth opening theme song. The B-side on the single is "Hatten×Joy".
The Single V version of "Hapi Hapi Sunday!" was released on February 11, 2009.