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.
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.
The name “Balmoral”, as applied to this traditional headdress, appears to date from the late 19th century, and in 1903 a bluebonnet in traditional style but with a stiffened crown was adopted briefly by some Lowland regiments as full dress headgear. After the Second World War, while all other Scottish regiments chose the Glengarry, a soft blue Balmoral was adopted as full dress headgear by the Black Watch (Royal Highland Regiment) and was worn with the green no. 1 dress jacket and with khaki no. 2 or service dress. As part of the amalgamation of the Scottish regiments in 2006, the military Balmoral was done away with all battalions of the Royal Regiment of Scotland now wear the Glengarry.
Use of the Balmoral has been championed by songwriter Richard Thompson, who uses it on stage, in addition to its traditional place in Highland dress.