The Balmoral (more fully the Balmoral bonnet in Scottish English or Balmoral cap otherwise, and formerly called the Kilmarnock bonnet) is a traditional Scottish hat that can be worn as part of formal or informal Highland dress. Developed from the earlier blue bonnet, dating to at least the 16th century, it takes the form of a knitted, soft wool cap with a flat crown. It is named after Balmoral Castle, a royal residence in Scotland. It is an alternative to the similar and related (informal) Tam o' Shanter cap and the (formal or informal) Glengarry bonnet.
Originally with a voluminous crown, today the bonnet is smaller, made of finer cloth, and tends to be dark blue, black, or lovat green. Ribbons in, or attached to the back of, the band (originally used to secure the bonnet tightly) are sometimes worn hanging from the back of the cap. A regimental or clan badge is worn on the left-hand side, affixed to a silk or grosgrain ribbon cockade (usually black, white or red), with the bonnet usually worn tilted to the right to display this emblem. The centre of the crown features a toorie, traditionally red. Some versions have a diced band (usually red and white check) around the circumference of the lower edge.
As worn by Scottish Highland regiments the blue bonnet gradually developed into a stiffened felt cylinder, often decorated with an ostrich plume hackle sweeping over the crown from left to right (as well as flashes of bearskin or painted turkey hackles). In the 19th century this tall cap evolved into the extravagant full dress feather bonnet while, as an undress cap, the plainer form continued in use until the mid-19th century. By then known as the Kilmarnock bonnet, it was officially replaced by the Glengarry bonnet, which had been in use unofficially since the late eighteenth century and was essentially a folding version of the cylindrical military cap.