Walter Carruthers Sellar (27 December 1898 – 11 June 1951) was a Scottish humourist who wrote for Punch. He is best known for the 1930 book 1066 and All That, a tongue-in-cheek guide to "all the history you can remember," which he wrote together with R. J. Yeatman.
Sellar was born at Golspie in Sutherland, the descendant of Patrick Sellar who had taken a leading role in the Highland clearances. He won a scholarship to Fettes College where he was Head Boy in 1917. After serving briefly in World War I as a Second Lieutenant in the King's Own Scottish Borderers, he took a degree in modern history at Oriel College, Oxford (which, as recorded in 1066 and All That, was awarded through an aegrotat in 1922). It was at Oriel that he met his contemporary Yeatman, and struck up a lifelong friendship. Although the two produced brilliant work together, they were entirely different personalities: Sellar was somewhat shy and introverted, although he enjoyed acting. He wrote melancholy poetry in addition to dry humour.