"Sekaiichi Happy na Onna no Ko" (世界一HAPPYな女の子?, "The happiest girl in the world") is the 17th major single by the Japanese idol group Cute, released in Japan on September 7, 2011 on the Zetima label.
The single will be released in three versions: Regular Edition (catalog number EPCE-5816), and Limited Editions A (EPCE-5812/3) and B (EPCE-5814/5) that include a bonus DVD. Limited Edition A DVD will contain the "Sekaiichi Happy na Onna no Ko (Dance Shot Ver.)" music video, and Limited Edition B will have "Sekaiichi Happy na Onna no Ko (Color Box Ver.)".