Z
- Sylas Neville (1741–1840) (diary 1767–1788)
- Stevie Nicks, singer/songwriter, member of Fleetwood Mac
- Harold Nicolson (1886–1968), British diplomat, politician and author
- Vaslav Nijinsky, Russian ballet dancer and choreographer (The Diary of Vaslav Nijinsky)
- Anaïs Nin, lover of Henry Miller, pornographer and poet: also known for her erotica
- James Oakes (1741–1829) (diary 1778–1827)
- Joyce Carol Oates, author
- Joe Orton, playwright
- Cynthia Ozick, author
- Michael Palin, member of Monty python, actor and travel writer
- Frances Partridge (née Marshall) (1900–2004), writer
- George S. Patton, US World War II General. Part of it was published by his wife after his death as War As I Knew It.
- Charles Willson Peale, Colonial American painter
- Emily Pepys (1833–1877). English child diarist (diary 1844–1845)
- Samuel Pepys, civil servant
- Elizabeth Percy, Duchess of Northumberland, 1716–1776
- Sylvia Plath, poet
- James K. Polk, 11th President of the United States
- Beatrix Potter English author of many children's books
- Hana Pravda actress and Holocaust survivor
- Dawn Powell, writer
- Barbara Pym, 20th century novelist
- Thomas Raikes
- Ronald Reagan 40th President of the United States
- Märta Helena Reenstierna (1753–1841)
- Henry Crabb Robinson (1775–1887)
- Ned Rorem, composer
- Henry Rollins, singer for Black Flag
- Everett Ruess, artist and poet who disappeared in the Utah Desert
- Dudley Ryder (1691–1756). Lord Chief Justice (diary 1715–1716)
- George Sand, writer
- May Sarton, poet and novelist
- Rudy Sarzo, rock bassist, most notably of Ozzy Osbourne fame
- Siegfried Sassoon, poet and author
- Marlene A. Schiwy, writer
- Sir Walter Scott, novelist
- Arthur M. Schlesinger, Jr., American historian and political adviser
- George Bernard Shaw, Nobel Prize-winning playwright
- Sei Shōnagon
- Emily Shore
- Malla Silfverstolpe, Swedish salon hostess
- Elizabeth Simcoe, Upper Canada in the 1790s
- Nikki Sixx, bassist/songwriter for Mötley Crüe
- Frances Stevenson, mistress and second wife of British Prime Minister David Lloyd George
- Joseph Stilwell, US World War II General. Published by his widow after his death as The Stilwell Papers.
- George Templeton Strong (1820–1875), New York lawyer
- Rosemary Sutcliff (1920-92) British historical novelist, and writer of children's and young adult books
- Henry Teonge (1620–1690), naval chaplain (diaries 1675–76 and 1678–79)
- Daniel Terdiman, award-winning journalist and diarist, published in both print and non-print media
- John Thomlinson (1692–1761), clergyman, (diary 1717–1722)
- Henry David Thoreau (1817–1862), author and philosopher
- Hester Thrale (1740–1821), author, friend and confidante of Samuel Johnson
- Sophia Tolstoy, wife of Russian author Leo Tolstoy: they read each other's diaries
- Marina Ivanovna Tsvetaeva, poet and writer
- Anne Truitt, artist
- Harry S. Truman, 33rd President of the United States
- Thomas Turner (diarist and shopkeeper), 1729–1793
- Marie Vassiltchikov, Russian princess, involved in plot to kill Adolf Hitler
- Victoria of the United Kingdom, 19th century monarch of the UK.
- Alice Walker, author
- Cosima Wagner, daughter of Franz Liszt, second wife of Richard Wagner
- Richard Wagner, composer
- Ralph Ward, Yorkshire cattle-dealer (diary 1754–1756)
- Sabrina Ward Harrison
- Andy Warhol, artist
- Simone Weil, philosopher
- Denton Welch, author
- Opal Whiteley, author, naturalist and subject of several books, including one by Benjamin Hoff
- Elie Wiesel, author
- Kenneth Williams, comic actor
- Lieutenant-General Adam Williamson (1676–1747), deputy lieutenant of the Tower of London, (diary 1722–1747)
- Edmund Wilson, writer and critic
- Otto Wolf, hid from the Nazis during World War II
- James Woodforde, eighteenth century English clergyman
- Wilford Woodruff, fourth President of The Church of Jesus Christ of Latter-day Saints
- Virginia Woolf, author and feminist
- Dorothy Wordsworth, poet, sister of William Wordsworth
- Zina D. H. Young, third President of the Relief Society of The Church of Jesus Christ of Latter-day Saints
Read more about this topic: List Of Diarists, N