The 225th Mixed Brigade (Spanish: 225.ª Brigada Mixta), was a mixed brigade of the Spanish Republican Army in the Spanish Civil War. It was formed in the summer of 1937 in Valencia with units belonging to the Eastern and had four battalions, the 897, 898, 899 and 900. In early March 1938 this mixed brigade was sent to the front in Aragon where it did not fare well. It suffered so many losses that it was disbanded. Later it was reorganized and was sent to Extremadura, to one of the last combats of the Civil War in 1939 before the Spanish Republic was defeated by the rebel faction.