Halloy may refer to:

Jean Baptiste Julien d'Omalius d'Halloy (1783–1875), Belgian geologist Halloy, Oise, a French commune Halloy, Pas-de-Calais, a French commune Château de Halloy, a castle in Halloy, Belgium Halloy, Belgium, a village in Belgium See also Halloy-lès-Pernois, Somme, a French commune