Juan Vázquez de Mella y Fanjul (1861–1928) was a Spanish politician and a political theorist. He is counted among the greatest Traditionalist thinkers, at times considered the finest author of Spanish Traditionalism of all time. A politician active within Carlism, he served as a longtime Cortes deputy and one of the party leaders. He championed an own political strategy, known as Mellismo, which led to secession and formation of a separate grouping.

Traditionalism is a Spanish political doctrine formulated in the early 19th century and developed until today. It understands politics as implementing the social kingship of Jesus Christ, with Catholicism as the state religion and Catholic religious criteria regulating public morality and every legal aspect of Spain. In practical terms it advocates a loosely organized monarchy combined with strong royal powers, with some checks and balances provided by organicist representation, and with society structured on a corporative basis. Traditionalism is an ultra-reactionary doctrine; it rejects concepts such as democracy, human rights, constitution, universal suffrage, sovereignty of the people, division of powers, religious liberty, freedom of speech, equality of individuals, and parliamentarism. The doctrine was adopted as the theoretical platform of the Carlist socio-political movement, though it appeared also in a non-Carlist incarnation. Traditionalism has never exercised major influence among the Spanish governmental strata, yet periodically it was capable of mass mobilization and at times partially filtered into the ruling practice.