The Diary of Lady Murasaki (紫式部日記, Murasaki Shikibu Nikki) is the title given to a collection of diary fragments written by the 11th-century Japanese Heian era lady-in-waiting and writer Murasaki Shikibu. It is written in kana, then a newly-developed writing system for vernacular Japanese, more common among women, who were generally unschooled in Chinese. Unlike modern diaries or journals, 10th-century Heian diaries tend to emphasize important events more than ordinary day-to-day life and do not follow a strict chronological order. The work includes vignettes, waka poems, and an epistolary section written in the form of a long letter.
The diary was probably written between 1008 and 1010 when Murasaki was in service at the imperial court. The largest portion details the birth of Empress Shōshi's (Akiko) children. Shorter vignettes describe interactions among imperial ladies-in-waiting and other court writers, such as Izumi Shikibu, Akazome Emon and Sei Shōnagon. Murasaki includes her observations and opinions throughout, bringing to the work a sense of life at the early 11th century Heian court, lacking in other literature or chronicles of the era.
A Japanese picture scroll, the Murasaki Shikibu Nikki Emaki, was produced during the Kamakura period (1185–1333), and the fragments of the diary serve as the basis for three important translations to English in the 20th century.