| Unit Name: | 91st Mixed Brigade |
| Native Name: | 91.ª Brigada Mixta |
| Start Date: | March 1937 |
| End Date: | March 1939 |
| Allegiance: | Republican faction |
| Branch: | Spanish Republican Army |
| Type: | Infantry |
| Specialization: | --> |
| Size: | Brigade |
| Colours: | --> |
| Colours Label: | --> |
| Battles: | Spanish Civil War |
| Notable Commanders: | Olegario Pachón Núñez |
The 91st Mixed Brigade was a unit of the Spanish Republican Army that took part in the Spanish Civil War. Throughout the war the brigade was present on the Extremadura front, attached to the 37th Division.
The unit was created in March 1937, from troops from the 20th Mixed Brigade, as well as the "Extremadura" battalions No. 1 and No. 2, and two battalions that had been created in the Extremaduran town of Campanario. It was under the command of Juan García Pina, with the anarcho-syndicalist Germán Clemente de la Cruz as political commissar. The Brigade was integrated into the 37th Division of the VII Army Corps.
Shortly after its creation, it was sent to participate in the Siege of Santuario de Nuestra Señora de la Cabeza, along with other republican brigades. Then she was sent to the Extremadura front, to participate in "Plan P". During the following months, Juan Bautista Gómez Ortiz and Ignacio López Montilla held command of the brigade, the 91st Brigade held defensive positions, without taking part in military operations.
In July 1938, at the beginning of the nationalist offensive on the Extremadura front, the 91st Mixed Brigade was located opposite Peraleda del Zaucejo. After the start of the fighting, the head of the unit, Ignacio López Montilla, was taken prisoner by the nationalists, having to be replaced by Copérnico Ballester Francés; but Ballester was wounded during the fighting, so the command of the brigade passed to Olegario Pachón Núñez. Around July 20, the 91st MB defended the southern front of the Mérida pocket, in Guareña. After concentrating on La Coronada, on July 23 it tried to reconquer Castuera, without success. The next day it was taken inside the pocket, together with the 20th Mixed Brigade. On July 25, the head of the VII Army Corps authorized the brigade to retreat towards the Zújar river, but the authorization came too late. The brigade was practically destroyed.
. José Manuel Martínez Bande . La batalla de Pozoblanco y el cierre de la bolsa de Mérida. 1981 . Editorial San Martín . Madrid.