Walter Weedon Grossmith, better known as Weedon Grossmith, was an English writer, painter, actor, and playwright best known as co-author of The Diary of a Nobody (1892) with his brother, music hall comedian and Gilbert and Sullivan star George Grossmith. Weedon Grossmith also illustrated The Diary of a Nobody to much acclaim.

The Diary of a Nobody is an English comic novel written by the brothers George and Weedon Grossmith, with illustrations by the latter. It originated as an intermittent serial in Punch magazine in 1888–89 and first appeared in book form, with extended text and added illustrations, in 1892. The Diary records the daily events in the lives of a London clerk, Charles Pooter, his wife Carrie, his son William Lupin, and numerous friends and acquaintances over a period of 15 months.