Don Carlos Manuel Mariano Martínez de Irujo y del Alcázar, 8th Duke of Sotomayor, 3rd Marquess of Casa Irujo, Grandee of Spain (3 April 1846 – 14 September 1909) was a Spanish noble and politician who was an influential figure of the Restoration and of the regency of Queen María Cristina.

On 24 December 1890, King Alfonso XIII of Spain granted the accompanying dignity of Grandee to Don Carlos as third marquis.

[6] He held various positions, including a member of the Congress of Deputies in 1876 and 1879 for the district of Ciudad Rodrigo with the ultramontane faction, and a Senator for the Logroño province in 1884 and, in his own right, since 1880.

Before her death on 7 September 1897, they were the parents of eleven children, four of whom died at an early age, including:[3] On 11 March 1899, he married María del Pilar Caro y Széchényi (1864–1931), younger sister of his first wife and widow of the Marquess of San Felices, José María Guillamas y Piñeiro, Grandee of Spain, who died in 1895.

[3] After his death, his widow, María del Pilar, remarried for the third time to the 12th Marquess of Martorell on 24 March 1922.