Captal de Buch (later Buché; from Latin capitalis, "first", "chief") was a medieval feudal title in Gascony held by Jean III de Grailly among others.

According to Du Cange, the designation captal (capital, captau, capitau) was applied loosely to the more illustrious nobles of Aquitaine, counts, viscounts, &c., probably as capitales domini, "principal lords", though he quotes more fanciful explanations. As an actual title, the