The Distinguished Service Order (DSO) is a military decoration of the United Kingdom, as well as formerly of other parts of the Commonwealth, awarded for operational gallantry for highly successful command and leadership during active operations, typically in actual combat. Since 1993 it has been awarded specifically for "highly successful command and leadership during active operations", with all ranks being eligible.^[5] It is a level 2A decoration (order) in the British system of military decorations.

Instituted on 6 September 1886 by Queen Victoria in a royal warrant published in The London Gazette on 9 November,^[7] the first DSOs awarded were dated 25 November 1886.^[8]

The order was established to reward individual instances of meritorious or distinguished service in war. It was a military order, until recently for officers only and typically awarded to officers ranked major (or equivalent) or higher, with awards to ranks below this usually for a high degree of gallantry, just short of deserving the Victoria Cross.^[9]

Whilst normally given for service under fire or under conditions equivalent to service in actual combat with the enemy, a number of awards made between 1914 and 1916 were under circumstances not under fire, often to staff officers, causing resentment among front-line officers. After 1 January 1917, commanders in the field were instructed to recommend this award only for those serving under fire.^[10]

From 1916, ribbon bars could be authorised for subsequent awards of the DSO, worn on the ribbon of the original award.^[10]

In 1942, the award was extended to officers of the Merchant Navy who had performed acts of gallantry whilst under enemy attack.^[11]

Prior to 1943, the DSO could be awarded to only commissioned officers of the Lieutenant-Colonel rank and above, for 'meritorious or distinguished service in wartime' under conditions of actual combat. If awarded to an officer ranking below Lieutenant-Colonel, it had to be a case of 'a high degree of gallantry just short of deserving the Victoria Cross'. In either case, being 'Mentioned in Dispatches' was a pre-condition for the award of a DSO.^[12]

A requirement that the order could be given only to someone mentioned in despatches was removed in 1943.^[10]

Since 1993, reflecting the review of the British honours system which recommended removing distinctions of rank in respect of operational awards, the DSO has been open to all ranks, with the award criteria redefined as "highly successful command and leadership during active operations".^[5] At the same time, the Conspicuous Gallantry Cross was introduced as the second-highest award for gallantry.^[13] Despite some very fierce campaigns in Iraq and Afghanistan, the DSO has yet to be awarded to a non-commissioned rank.^{[citation needed]}

The DSO had also been awarded by Commonwealth countries but by the 1990s most, including Canada, Australia and New Zealand, were establishing their own honours systems and no longer recommended British honours.^[14]

Recipients of the order are officially known as Companions of the Distinguished Service Order, and are entitled to use the post-nominal letters "DSO". All awards are announced in The London Gazette.^[15]

• The medal signifying the award of the DSO is a silver-gilt (gold until 1889) cross with curved ends, 1.6 in (4.1 cm) wide, enamelled white and edged in gilt.^[3] It is manufactured by Messrs Garrard & Co, the Crown Jewellers.^[15]
• In the centre of the obverse, within a green enamelled laurel wreath, is the imperial crown in gold upon a red enamelled background. The reverse has the royal cypher of the reigning monarch in gold within a similar wreath and background.^[15]
• A ring at the top of the medal attaches to a ring at the bottom of a gilt suspension bar, ornamented with laurel. Since 1938 the year of award engraved on the back of the suspension bar.^[15] At the top of the ribbon is a second gilt bar ornamented with laurel.^[9]
• The medals are issued unnamed but some recipients have had their names engraved on the reverse of the suspension bar.^[9]
• The red ribbon is 1.125 in (2.86 cm) wide with narrow blue edges.^[13]
• The bar for an additional award is plain gold with an Imperial Crown in the centre. Since about 1938, the year of the award has been engraved on the back of the bar.^[15] A rosette is worn on the ribbon in undress uniform to signify the award of each bar.^[16]

• Military awards and decorations of the United Kingdom
• Orders, decorations, and medals of the Commonwealth realms