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- Saari – consolidated with Parikkala and Uukuniemi to form Parikkala in 2005
- Sahalahti – became part of Kangasala in 2005
- Säkkijärvi – was partially lost to the USSR in 1944, the rest was incorporated into Miehikkälä and Ylämaa in 1946
- Sakkola – was lost to the USSR in 1944
- Salmi – was lost to the USSR in 1944
- Saloinen (known as Salo until 1913) – became part of the City of Raahe in 1973
- Sammatti – consolidated with Lohja in 2009
- Sastamala – the old name of Karkku. The name was re-introduced in 2009, when Äetsä, Mouhijärvi and Vammala were consolidated.
- Savonranta – consolidated with Savonlinna in 2009
- Säyneinen – became part of Juankoski in 1971
- Seinäjoen maalaiskunta – became part of Seinäjoki in 1959
- Seiskari – was lost to the USSR in 1944
- Sideby – became part of the City of Kristinestad in 1973
- Simpele – was partially lost to the USSR in 1944, the rest was incorporated into Rautjärvi in 1973
- Sippola – was consolidated with Anjala to form Anjalankosken kauppala in 1975
- Snappertuna – most of the municipality was incorporated into Ekenäs and the rest into Karis in 1977
- Somerniemi – became part of Somero in 1977
- Soanlahti – was lost to the USSR in 1944
- Solf – the part on the mainland became part of Korsholm in 1973
- Sortavala – was lost to the USSR in 1944
- Sortavalan mlk – was lost to the USSR in 1944
- Suistamo – was lost to the USSR in 1944
- Sumiainen – became part of City of Äänekoski together with Suolahti in 2007
- Sundom – became part of the City of Vaasa in 1973
- Suodenniemi – became part of City of Vammala in 2007
- Suojärvi – was lost to the USSR in 1944
- Suolahti – became part of City of Äänekoski together with Sumiainen in 2007
- Suomusjärvi – consolidated with Salo in 2009
- Suoniemi – became part of the City of Nokia in 1973
- Suursaari – was lost to the USSR in 1944
- Särkisalo – consolidated with Salo in 2009
- Säräisniemi – a part of Utajärvi was annexed to Säräisniemi to form the municipality of Vaala in 1954
- Säynätsalo – became part of the City of Jyväskylä in 1993
- Sääksmäki – became part of Valkeakoski in 1973
- Sääminki – most of the municipality was incorporated into Savonlinna and the rest into Punkaharju in 1973
Read more about this topic: Former Municipalities Of Finland