A sash ( , shashCraig, 1849, p. 620) is a cloth belt used to hold a robe together, and is usually tied about the waist. The Japanese equivalent of a sash, obi, serves to hold a kimono or yukata together. Decorative sashes may pass from the shoulder to the hip rather than around the waist. Sash is an Arabic loanword that was introduced into the English language in 1590.Metcalf, 1999, p. 123.

Sashes traditionally form part of formal military attire (compare the sword-belt known as a baldric, and the cummerbund). Most of the European Royal families wear sashes as a part of their royal (and/or military) regalia. Some Order (decoration)s such as the Légion d'honneur include sashes as part of the seniormost grades' insignia. In Latin America and some countries of Africa, a special presidential sash indicates a president's authority. In France and Italy, sashes, featuring the national flag tricolours and worn on the right shoulder, are used by public authorities and local officials; likewise Italian military officers wear plain blue sashes on the right shoulder during ceremonial occasions.

Sashes are a distinctive feature of the modern French Army for parade dress. They are worn around the waist in either blue or red by corps such as the Foreign Legion, the Spahis, the Chasseurs d' Afrique and the Tirailleurs which were originally raised in North Africa during the period of French colonial rule. In its traditional Franco-Algerian or zouave form the sash ("ceinture de laine") was four metres in length and forty centimetres in width.

At the time of the American Civil War (1861-65) red sashes were authorised for officers and sergeants of the regular US Army (Army Regulations of 1861). U.S. Generals continued to wear buff silk sashes in full dress until 1917. In the Confederate Army of the Civil War period sash colour indicated the corps or status of the wearer. For example: gold for cavalry, burgundy for infantry, black for chaplains, red for sergeants, green or blue for medics, and grey or cream for general officers.

The modern British Army retains a scarlet sash for wear by sergeants in certain orders of dress, over the right shoulder to the hip. A similar burgundy sash is worn around the waist by officers of the Foot Guards in scarlet full dress and officers of line infantry in dark blue "Number 1" dress. The same practice is followed in some Commonwealth armies.

The present day armies of India and Pakistan both make extensive use of waist sashes for ceremonial wear. The colours vary widely according to regiment or branch and match those of the turbans where worn. Typically two or more colours are incorporated in the sash, in vertical stripes. One end hangs loose at the side and may have an ornamental fringe. The practice of wearing distinctive regimental sashes goes back to at least the nineteenth century.