Casimiro Alegre (1741–1825) was an Argentine politician and military man, who had an outstanding participation during the Viceroyalty of Peru and Viceroyalty of the Río de la Plata, serving as alcalde of campaign in the Province of Buenos Aires, and as Commandant in the Regiment of Blandengues of the Frontier of Buenos Aires. He participated in military expeditions against the Indians prior to the Desert Campaign of the 1830s. He was one of the landowners of Buenos Aires who supported the Independence movements of Argentina.