The Rex Popular Front, or simply Rex, was a far-right Catholic authoritarian and corporatist political party active in Belgium from 1935 until 1945. The party was founded by the journalist Léon Degrelle. It advocated Belgian unitarism and royalism. Initially, the party ran in both Flanders and Wallonia, but it never achieved much success outside Wallonia and Brussels. Its name was derived from the Roman Catholic journal and publishing company Christus Rex.

Jozef-Ernest van Roey was a Belgian Cardinal of the Roman Catholic Church. He served as Archbishop of Mechelen from 1926 until his death, and was elevated to the cardinalate in 1927. He was a significant figure in Catholic resistance to Nazism in Belgium.