Diary of Samuel Pepys, M. A. , F. R. S. , Clerk of the Acts and Secretary to the Admirality : Pepysiana, or, Additional Notes on the Particulars of Pepys's Life and on Some Passages in the Diary

Samuel Pepys (23 February 1633 – 26 May 1703) was an administrator of the navy of England and Member of Parliament.

The detailed private diary that Pepys kept from 1660 until 1669 is one of the most important primary sources for the English Restoration period. It provides a combination of personal revelation and eyewitness accounts of great events, such as the Great Plague of London, the Second Dutch War, and the Great Fire of London. Pepys recorded his daily life for almost ten years. Pepys has been called the greatest diarist of all time due to his frankness in writing concerning his own weaknesses and the accuracy with which he records events of daily British life and major events in the 17th century. Pepys wrote about the contemporary court and theater, his household, and major political and social occurrences.

Historians have been using his diary to gain greater insight and understanding of life in London in the 17th century. Pepys wrote consistently on subjects such as personal finances, the time he got up in the morning, the weather, and what he ate. He talked at length about his new watch which he was very proud of (and which had an alarm, a new thing at the time), a country visitor who did not enjoy his time in London because he felt that it was too crowded, and his cat waking him up at one in the morning. Pepys's diary is one of the only known sources which provides such length in details of everyday life of an upper-middle-class man during the seventeenth century. His diary reveals his jealousies, insecurities, trivial concerns, and his fractious relationship with his wife. It has been an important account of London in the 1660s.

Aside from day-to-day activities, Pepys also commented on the significant and turbulent events of his nation. England was in disarray when he began writing his diary. Oliver Cromwell had died just a few years before, creating a period of civil unrest and a large power vacuum to be filled. Pepys had been a strong supporter of Cromwell, but he converted to the Royalist cause upon the Protector’s death. He was on the ship that brought Charles II home to England. He gave a firsthand account of events, such as the coronation of King Charles II and the Restoration of the British Monarchy to the throne, the Anglo-Dutch war, the Great Plague, and the Great Fire of London.