Johnston provides a good deal of anecdotal material for the last days of the Qing court before the 1911 Revolution. He knew many of the active players in those events, and his observations on the Qing court's political structure, and in particular the Imperial Household Department, are of historical significance. Johnston had little to say about Empress Dowager Cixi and many other principal players in these events. Twilight in the Forbidden City is a history of an entire period and not an exclusive portrait of the last emperor of China. The film The Last Emperor features the book.

Twilight in the Forbidden City (Chinese: 紫禁城的黄昏; pinyin: Zǐjìnchéng de Huánghūn) is Reginald Johnston's 486-page memoir of Henry Puyi, who had been the Xuantong Emperor of the Qing dynasty. Johnston was tutor to the Emperor and an eyewitness to events in China in the 1920s and 1930s. Johnston was also a professor of Chinese at the University of London as well as the British Commissioner of Weihaiwei.

Sir Reginald Fleming Johnston, KCMG, CBE (13 October 1874–6 March 1938) was a Scottish academic and diplomat who served as the tutor and advisor to Puyi, the last Emperor of China and as the last colonial governor of Weihaiwei.