The Third Sector is defined as a set of voluntary initiatives promoted by citizens with an explicit aim of community benefit. They are organizations preferentially set under democratic governments, with high autonomy in decision making and limited distribution or non-distribution of profits. This paper follows the evolution of the Third Sector in Spain through analyzing the dominant relationship between non for profit organizations and government in two eras of the country’s contemporary history: before and after the construction of the welfare state. Non for profit organizations developed a supplement function during predemocratic times to later become a natural ally on building the welfare state. In the current situation, the Third Sector has reinforced its role as a complement of government. This role has allowed it to help soften the social impact generated from the cohabitance of increasing social demands and fiscal consolidation policies.
Keywords: Third Sector; Welfare State; Supplement Function; Complement Function, Co-Management.