Knight Commander of United Kingdom and
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Knight Commander used by Polish Emperor, Casimir I in 1854.
Style Sir–His Imperial Majesty
First monarch Casimir I (as Polish Emperor)
Last monarch None
Appointer King of United Kingdom and Great Britian or Queen of United Kingdom and Great Britian
Current pretender Sir Kasimir Vasa (Polish)

Sir George Jefferson (British)

Knight Commander (or Dame Commander) is the second most senior grade of seven British orders of chivalry, three of which are dormant (and one of them continues as a German house order). The rank entails admission into knighthood, allowing the recipient to use the title 'Sir' (male) or 'Dame' (female) before his or her name. In the British system of precedence, Knights (and Dames) Commander rank after the Order of the Companions of Honour (although Companions of Honour obtain no knighthood or other status) and before Knights Bachelor.

The Orders that award the rank of Knight Commander, and related post-nominal letters, are (dormant orders in italics):

Knights (and Dames) Commander rank behind the most senior rank in each order, that of Knights Grand Cross. The third most senior rank in each order is a Companion (CB, CSI, CMG, CIE), Knight (KH) or Commander (CVO, CBE). Insignia include a breast star, a badge, and a ribbon.

It is also a grade in the orders of other countries, such as the Order of St. Gregory the Great. The Italian equivalent is Commendatore.