Scholars have long argued that democratic forces—electoral and interest group pressures—should lead to the adoption of social legislation entitling many social groups to welfare benefits. However, contrary to the theoretical expectations, authoritarian governments have pioneered social insurance legislation: more than two-thirds of laws regulating insurance against old age, sickness, disability, and unemployment have originated in authoritarian regimes and some of these laws have covered broad social and occupational groups. In the absence of electoral and interest group pressures then, what motivates some authoritarian regimes to promulgate comprehensive social legislation? To answer this question, I investigate the origins of social legislation in three authoritarian regimes—Egypt, Tunisia, and Turkey. I argue that comprehensive social legislation originates from the presence of Integral Mass Parties (IMPs) during the foundational moments of authoritarian regimes. IMP’s presence generates two pathways to the promulgation of comprehensive social legislation: (1) When IMPs take over a regime after gaining independence, they seek to radically transform the societies they rule by injecting national identities into socially diverse societies, changing the power dynamics at the local level, and altering even the everyday life practices. These transformative goals require them to win the consent of the masses for their hegemonic projects which in turn pushes them to entitle diverse social groups to welfare benefits. (2) When IMPs do not govern but stand as contenders for power during foundational moments, they push the founding elites to incorporate mass actors into the governing coalitions which in turn leads to the enactment of comprehensive social legislation. To provide evidence for these arguments, my comparative historical analysis draws on extensive archival materials from the Egyptian, Tunisian, and Turkish national archives and covers the span of 1920-1975. Drawing an original database, I also test the implications of my arguments in the Middle East and North Africa region and show that IMPs pioneered the promulgation of comprehensive social programs and these programs have persisted over time.