A sailor dress is a child's or woman's dress that follows the styling of the sailor suit, particularly the bodice and collar treatment. A sailor-collared blouse is called a middy blouse ("middy" derives from "midshipman").^[1] In early 20th-century America, sailor dresses were very popularly known as Peter Thomson dresses after the former naval tailor credited with creating the style.^[2]

Peter Thomson (sometimes spelled Thompson)^[3] had tailoring establishments in New York and Philadelphia in around 1900.^[4] His original sailor dresses and suits, for both women and children (including young boys), are represented in several American museum collections including the Metropolitan Museum's Costume Institute,^[5] and the Philadelphia Museum of Art.^[6] The 'Peter Thomson dress' was made from cotton or linen for summer wear, or wool in winter.^[7] It was promoted as an ideal costume or uniform for female students and schoolchildren, and was popular with those trying to establish a "standardized style" of clothing.^[8][9] By 1919, the Peter Thomson dress was regarded as a valid option for school uniforms, and was described as synonymous with "good taste for girls of 14-18 years old for many years."^[9] Peter Thomson styling was also applied to the bodices of early bathing costumes.^[10]

Dresses with sailor styling were known before the Peter Thomson design took hold. In Sweden in 1887, a sailor dress with natural waist and pleated skirt was among the designs promoted by the dress reform movement as appropriate for young girls.^[11]

Although sailor styling is sometimes seen on women's dresses, since the mid-20th century it is mainly associated with dresses for babies and small children.^[12] During the late 20th century sailor styling became associated with maternity dresses, which has led to some negativity towards sailor styles for womenswear and the general idea of a woman dressing 'like a child'.^[13] The maternity clothing designer Liz Lange declared "She shouldn't have to dress like a child just because she's having a child; it's one thing to put a toddler in a sailor suit but it's another thing completely to condemn a grown woman to such a fate."^[14]

• Japanese school uniform
• Sailor hat