The sailor outfit or sailor fuku is a common Japanese school uniform (セーラー服 sērā-fuku) worn by middle school and high school students. It was introduced as a school uniform in 1921 by the principal of Fukuoka Jo Gakuin University (福岡女学院), Elizabeth Lee. It was modelled after the uniform used by the British Royal Navy at the time, which she herself had experienced as an exchange student in the U.K.

Much like the male uniform, the gakuran, Sailor-fuku bears similiarity to various military styled naval uniforms. The uniform generally consists of a blouse attached with a sailor-style collar (襟 eri) and a pleated skirt. There are seasonal variations for summer and winter for which sleeve length and fabric are adjusted accordingly. A ribbon is tied in the front and laced through a loop attached to the blouse. Several variations on the ribbon include neck ties, bolo ties, and bows. Common colors are navy blue, white, grey, and black.

Shoes, socks, and other accessories are sometimes included as part of the uniform. Accompanying socks are typically navy or white and accompanying shoes are typically brown or black penny loafers. Although they are not part of the prescribed uniform, loose socks are also commonly matched by more fashionable girls with their sailor fuku.

Sailor fuku has a nostalgic charactistic for former students and is often associated with relatively carefree youth. Immitation Sailor Fuku is a popular costume for Halloween and other party events and is sold at department stores and costume shops throughout Japan.

Because the Sailor Fuku is a popular fetish item, actual pre-worn second-hand uniforms are brokered through underground establishments known as burusera although changes to Japanese law have since made such practices difficult.

The uniform in general is seen by some youth as a symbol of conformity and as such has been modified by rebellious students as a means of exhibiting individualism. Such variations include lengthening or shortening the skirt, rolling up the sleeves, removing the ribbon, hiding patches or badges under the collar, etc. In past decades, brightly colored varients of Sailor Fuku were also adopted in the by Japanese yankee and Bousouzoku biker gangs.

Sailor Fuku also plays an undeniably large role in otaku culture and the Japanese sexual canon as evidenced by the large amount of anime, manga, and doujinshi featuring characters in uniform. Some examples:

• The anime Sailor Moon, in which the characters all wear elaborate Sailor Fuku uniforms when they transform into super heroines.
• "Sailor Fuku" was a popular song by the Onyanko club in the 1980's.
• The popular television and movie series Sukeban Deka features delinquent teenage girls

• Gakuran
• Japanese school uniform