"Happiness" is the twentieth single by Japanese boy band, Arashi, as well as its title song's name. The single was released on September 5, 2007, in two editions: a regular edition containing the karaoke versions of the songs released in the single, and a limited edition containing a bonus track. The single is the group's ninth consecutive and seventeenth overall number one release, as well as their third consecutive English-titled release.

Arashi is a Japanese boy band consisting of five members formed under the Johnny & Associates talent agency. The members are Satoshi Ohno, Sho Sakurai, Masaki Aiba, Kazunari Ninomiya, and Jun Matsumoto. Arashi officially formed on September 15, 1999, in Honolulu, Hawaii, and made their debut CD on November 3, 1999. The group was initially signed to Pony Canyon and released one studio album and six singles—beginning with their 1999 eponymous debut single before moving to the Johnny's subsidiary label J Storm in 2001, which was initially set up for their succeeding releases. While their debut single sold close to a million copies, the group took a mixture of pop and alternate/contemporary approach to its music which attracted core followers, but subsequently faced commercially slow sales.