José María Justo Cos y Macho (6 August 1838 – 17 December 1919) was a Spanish Cardinal of the Roman Catholic Church who served as Archbishop of Valladolid from 1901 until his death, and was elevated to the cardinalate in 1911.

He studied at the Jesuit School in Segura, Seminary of Monte Corbán in Santander, and the University of Salamanca, where he obtained his doctorate in theology.

He received his episcopal consecration on the following 12 September from Archbishop Victoriano Guisasola y Rodríguez, with Bishops Ramón Martínez Vigil, OP, and José Mazarrasa y Rivas serving as co-consecrators, in the Cathedral of Oviedo.

Cos was promoted to Archbishop of Santiago de Cuba on 14 February 1889 and served as a senator of the Spanish Kingdom from 1891 until his death.

Between the death of Joaquín Beltrán y Asensio on 3 November 1917 and the appointment of Enrique Pla y Deniel on 4 December 1918, he served as Apostolic Administrator of Ávila.