The Constitution of Finland (Suomen perustuslaki or Finlands grundlag) is the supreme source of national law of Finland. It defines the basis, structures and organisation of government, the relationship between the different constitutional organs, and lays out the fundamental rights of Finnish citizens, and individuals in general. The original Constitution Act was enacted in 1919, soon after Finland declared its independence in 1917. The current draft of the Constitution came into force on 1 March 2000.
Finland's current constitutional provisions are enshrined in a single statute: the Constitution of Finland (731/1999).
Before the enshrinement, the Finnish constitutional provisions were divided between four separate statutes, which all had a constitutional status; the Constitution Act of 1919 (Suomen hallitusmuoto), Parliament Act of 1928 (valtiopäiväjärjestys), the Ministerial Responsibility Act of 1922 (laki eduskunnan oikeudesta tarkastaa valtioneuvoston jäsenten ja oikeuskanslerin sekä eduskunnan oikeusasiamiehen virkatointen lainmukaisuutta, short title ministerivastuulaki) and the Act on the High Court of Impeachment of 1922 (laki valtakunnanoikeudesta). All these statutes were merged into a single constitution and repealed with the passage thereof.
The fundamental principles of the Constitution Act of 1919 and the Parliament Act of 1906, amended in 1928, remained unchanged during the first fifty years of Finnish independence, as there was little pressure or need for any amendments to the Constitution Act. However, this did not prevent the Constitution from adapting to the changing needs of the day. The flexibility of the Finnish Constitution is due to the use of "exceptive laws", a distinctive feature of the Finnish system: instead of amending or changing the Constitution, an act may be passed as an ad hoc exception to it. Such an exceptive law does not become part of the Constitution and it may be repealed like an ordinary act. Exceptive laws were formerly much used, even to the point of threatening to undermine respect for Constitutional provisions.