Pillarisation (verzuiling in Dutch) is a term used to describe the politico-denominational segregation of Dutch and Belgian society. These societies were (and in some areas, still are) "vertically" divided into several segments or "pillars" (zuilen, singular: zuil) according to different religions or ideologies. These pillars all had their own social institutions: their own newspapers, broadcasting organisations, political parties, trade unions, banks, schools, hospitals, universities, scouting organisations and sports clubs. Some companies even hired only personnel of a specific religion or ideology. This led to a situation where many people had no personal contact with people from another pillar.

The Netherlands had (at least) three pillars: Protestant, Catholic and Social-democratic. Almost all Catholics were part of the Catholic pillar. Orthodox and conservative Protestants joined the Protestant pillar, industrial workers and Jews were part of the Socialist pillar, while more latitudinarian Protestants, atheists and Orangists were pillarless. The Protestant party Christian Historical Union (formed in 1908) did not organise a pillar of its own but linked itself to the Protestant pillar shaped by the Anti Revolutionary Party. Pillarisation was originally initiated by the Anti Revolutionary Party, who based it on their philosophy of sphere sovereignty. People in the Socialist pillar were mainly working-class. People who were not associated with one of these pillars, mainly middle and upper class latitudinarian Protestants and atheists set up their own pillar: the general pillar. Ties between general organisations were a lot weaker. The political parties usually associated with this pillar were the liberal Free-minded Democratic League (VDB) and Liberal State Party (LSP), although these parties opposed pillarisation. Communists, Humanist and ultra-orthodox Protestants also set up similar organisations; however, such groups were a lot smaller.