The concept of ‘Czechoslovakism’ can be regarded as being both an ideology, which holds that the Czechs and the Slovaks comprise one nation, and a political programme designed to result in the unification of both nations in one state. Czechoslovakism as a political programme was first formulated during the First World War by the independence movement abroad, in order to justify the establishment of a Czechoslovak state, comprising the Czech Lands and Slovakia. The idea that the Czechs and Slovaks were twin aspects of a single nation had a far older pedigree, going back to the national revivals of the late eighteenth and early nineteenth centuries. Czechoslovakist ideology had its heyday during the First Czechoslovak Republic (1918–1938), when it became the state doctrine, and it was officially abandoned after the Second World War. Czechoslovakism also existed in two versions: the first version held that Czechs and Slovaks jointly comprised a Czechoslovak nation formed from two tribes, Czechs and Slovaks; the second maintained that the Slovaks were actually less developed Czechs.

During the First Republic, the theory of a unitary Czechoslovak nation was closely associated with administrative centralism. While there was little Czech opposition to official Czechoslovakism, Slovakia's political elite were split over this issue and the majority opposed their imposition.

The purpose of this chapter is to examine the ideological composition of Czechoslovakism, and to give an overview of the role of Czechoslovakism in Slovak history.