An official history is a work of history

History

History is the discovery, collection, organization, and presentation of information about past events. History can also mean the period of time after writing was invented. Scholars who write about history are called historians...

 which is sponsored, authorised, or endorsed by its subject. The term is most commonly used for histories which are produced at a government's behest.

Governments have commissioned official histories for a range of purposes. These include promoting the government's achievements, reflecting on past practices, commemorating events and providing an authoritative record for other historians to draw from. Military history

Military history

Military history is a humanities discipline within the scope of general historical recording of armed conflict in the history of humanity, and its impact on the societies, their cultures, economies and changing intra and international relationships....

 is a particularly common topic for official histories to cover. Examples of official military histories include the Australian series Official History of Australia in the War of 1914–1918 and Australia in the War of 1939–1945 and the British series History of the Great War

History of the Great War

The History of the Great War is a series of 28 volumes covering the military operations of the British Army during the First World War. The full title is the History of the Great War Based on Official Documents but the series is usually referred to as the British Official History...

and History of the Second World War

History of the Second World War

The History of the Second World War is the official history of Britain's contribution to the Second World War and was published by Her Majesty's Stationery Office . This immense project was sub-divided into a number of areas to ease publication. Military operations are covered in the United Kingdom...

.