Applying for Finnish Citizenship

You can apply for Finnish citizenship if you are over 18, have had permanent residence in Finland for a sufficient amount of time and still reside in Finland. Proof of identity is required. You must also be able to present a plan of how you and your family intend to support yourselves. You also need to have knowledge of the Finnish or Swedish language, or alternatively Swedish or Finnish Sign Language. Language skills can be proven to be sufficient by obtaining level 3 in the National Board of Education Language Exam. 
Obtaining citizenship may be prolonged if you have committed a crime or failed to pay taxes or fines. Information on these requirements and their practical application can be obtained from the Finnish Immigration Service.
The Finnish Immigration Service provides citizenship application forms, which are available at the Immigration Police. Applications must be lodged with the police in person. Proof of identity is required. Citizenship applications are subject to a charge. The charge is payable beforehand, in connection with lodging the application.
Citizen application forms in English
Citizen application forms in Swedish
Citizen application forms in Finnish