Slughorn was the surname of a pure-blood wizarding family.
The Slughorns were included in the Pure-Blood Directory (published anonymously in Britain, although widely believed to have been authored by Cantankerus Nott), which listed them as one of the twenty-eight truly pure-blood families (the so-called 'Sacred Twenty-Eight').[1]
Among the family members was Horace Slughorn, Potions master and Head of Slytherin House in the 1940s and, after a brief retirement, again in the late 1990s.