Mellismo (Spanish: [meˈʎizmo]) was a political practice of Spanish ultra-Right of the early 20th century. Born within Carlism, it was designed and championed by Juan Vázquez de Mella, who became its independent political leader after the 1919 breakup. The strategy consisted of an attempt to build a grand ultra-Right party, which in turn would ensure transition from liberal democracy of Restauración to corporative Traditionalist monarchy. Following secession from Carlism Mellismo assumed formal shape of , but it failed as an amalgamating force and decomposed shortly afterwards. Theoretical vision of Mella is usually considered part of the Carlist concept and does not count as Mellismo; the strategy to achieve it does. In historiography its followers are usually referred to as Mellistas, though initially the term Mellados seemed to prevail. Occasionally they are also named Tradicionalistas, but the term is extremely ambiguous and might denote also other concepts.
Generally historiographical works do not refer to Mellismo or to Mellistas prior to 1910; press of the era started to use this term as late as 1919. When discussing internal groupings within Carlism in the early years of the 20th century, scholars refer to the faction more inclined towards alliances with other parties as "posibilistas", while those tending to side with a deposed leader marqués de Cerralbo are dubbed "cerralbistas"; this is also how Vázquez de Mella preferred to refer to himself. However, he started to gain supporters and admirers of his own already in the 1890s, initially lured by his charismatic oratory skills rather than by his theoretical vision or specific political strategy. In fact, his stand might have seemed puzzling: he declared himself enemy of the Restoration system but advocated political alliances with established parties, enthusiastically took part in electoral game but was engaged in conspiracy to stage military coup in 1898-1900, supported minimalist electoral coalitions but preached maximalist objectives, claimed doctrinal Traditionalist orthodoxy but remained in uneasy relationship with the king and revealed cautious penchant towards non-dynastical solutions.