In Finland, a person must have a surname and can have up to three given names. Surnames are usually inherited patrilineally, while given names are usually chosen by a person's parents. Finnish names come from a variety of dissimilar traditions that were consolidated only in the early 20th century. The first national act on names came into force in 1921, and it made surnames mandatory. Between 1930 and 1985, the Western Finnish tradition whereby a married woman took her husband's surname was mandatory. Previously in Eastern Finland, this was not necessarily the case.
In Finnish, the letter "j" denotes the approximant [j], as in English you. For example, the two different names Maria and Marja are pronounced nearly identically. The letter "y" denotes the vowel [y], not found in English, but similar to German "ü" and French "u". "R" is rolled. The stress is always on the first syllable in Finnish. For example, Yrjö Kääriäinen is pronounced [ˈyrjø ˈkæːri.æinen]. Double letters always stand for a geminate or longer sound (e.g., Marjaana has a stressed short [ɑ] followed by an unstressed long [ɑː]).
Pronunciation of Swedish names is similar, but long vowels are not doubled and the stress may be on any syllable. Finland has a long bilingual history and it is not unusual for Finnish speakers to have Swedish surnames or given names. Such names may be pronounced according to Finland–Swedish phonology or, depending on the person named, the person speaking and the language used, a Fennicized variant.
When writing Finnish names without the Finnish alphabet available (such as in e-mail addresses), the letters "ä" and "ö" are usually replaced with "a" and "o", respectively (e.g., Pääkkönen as Paakkonen). This is not the same, but visually recognizable; since they are not linguistically umlauts, they cannot be substituted with "ae" and "oe" as in German.
Finland has three predominant surname traditions: the West Finnish, the East Finnish and that of the Swedish nobility, clergy, bourgeoisie and military. Until the early 20th century, Finland was a predominantly agrarian society and the names of West Finns were based on their association with a particular area, farm, or homestead (e.g., Jaakko Jussila ("Jaakko from the farm of Jussi")). Farm names typically had the suffix -la and could refer to the husband (like Jussila) or describe the location (e.g., Isoaho "large clearing"). This name could change every time the person moved to a different farm. Also, even if one had a surname, one would still be better known by the farm name. Farm names, patronyms and village names could be used to disambiguate between different people, but they were not true inherited surnames. For example, in the novel Seven Brothers (Aleksis Kivi, 1870) the character Juhani was officially summoned as Juhani Juhanin-poika Jukola, Toukolan kylästä; "Juhani, son of Juhani, from Jukola farm, Toukola village".
On the other hand, the East Finnish surname tradition dates back to the 13th century. There, the Savonians pursued slash-and-burn agriculture which necessitated moving several times during a person's lifetime. This in turn required the families to have surnames, which were in wide use among the common folk as early as the 13th century. By the mid-16th century, the East Finnish surnames had become hereditary. Typically, the oldest East Finnish surnames were formed from the first names of the patriarchs of the families (e.g., Ikävalko, Termonen, Pentikäinen). In the 16th, 17th and 18th centuries, new names were most often formed by adding the place name of the former or current place of living (e.g., Puumalainen < Puumala). In the East Finnish tradition, women carried the family name of their fathers in female form (e.g., Puumalatar < Puumalainen). By the 19th century, this practice fell into disuse due to the influence of West-European surname tradition. Also, women did not change their surnames with marriage.
In 1921, surnames became compulsory for all Finns. At this point, if there was no surname, the homestead names were usually adopted as surnames. Because the inhabitants often included farmhands and other non-family, holders of the same surname are not necessarily genetically related. A typical feature of such names is the addition of prefixes Ala- or Ali- (Sub-) or Ylä- (Up-), giving the location of the holding along a waterway in relation of the main holding (e.g., Yli-Ojanperä, Ala-Verronen). In Pohjanmaa, there are similar prefixes Rinta- "downstream" and Latva- "upriver".
Common suffixes are -nen (in oblique form -se-; e.g., Miettinen—Miettisen "Miettinen's"), a diminutive suffix usually meaning "small", and -la/ -lä, a locative suffix usually meaning "place of". The -nen suffix was freely interchanged with -son or -poika as late as the 16th century, but its meaning was ambiguous as it could refer not only to a "son", but any member of a patriarch's family, a farm or even a place. For example the surname Tuomonen could mean "Son of Tuomo" or "Farm of Tuomo" or something else belonging to Tuomo.
A third tradition of surnames was introduced in Finland by the Swedish-speaking upper and middle classes which used typical German and Swedish surnames. By custom, all Finnish-speaking persons who were able to get a position of some status in urban or learned society, discarded their Finnish name, adopting a Swedish, German or (in case of clergy) Latin surnames.  In the case of enlisted soldiers, the new name was given regardless of the wishes of the individual. The oldest noble surnames of Swedish origin were not original, but were derived from the charges in the coat of arms, sigil and flag of the family, for example with Svärd (Swedish: "sword"), Kurki/Kurck (Finnish: "crane") and Kirves (Finnish: "axe").  Families of German origin would use the von suffix (e.g., von Wright).
In the late 19th and early 20th century, the overall modernization process and especially, the political movement of Fennicization caused a movement for adoption of Finnish surnames. At that time, many persons with a Swedish or otherwise foreign surname changed their family name to a Finnish one. The features of nature with endings -o/ö, -nen (Meriö < meri "sea", Nieminen < niemi "peninsula") are typical of the names of this era, as well as more or less direct translations of Swedish names (Helleranta < Hällstrand).  Fennicizing one's name also concealed non-Finnish origin.  For example, Martti Ahtisaari's grandfather was Adolfsen from Norway. Nevertheless, Fennicization was not mandatory and thus it is common to find entirely Finnish-speaking families with Swedish surnames; having a Swedish name does not imply that one would speak Swedish.
An effect of industrialization was that large numbers of people moved to the cities and towns and had to adopt a surname. Missing an inherited surname, they invented one from scratch. Initially, these were in Swedish, and they were not very stable; people called them "superfluous names" (liikanimi), and a person could change one's surname several times during their career. Later, Finnish became the preferred language, and themes were taken from nature. Some of the most common examples of this type are Laine "comber, wave", Vainio "cultivated field", Nurmi "grassland", and Salo "grove".  When applicable, -nen or -la/-lä could be suffixed, such as in Koskinen "rapids + nen".
|1||Korhonen||korho "deaf" or "proud"||23,509|
|6||Hämäläinen||Häme " Tavastia"||19,242|
|8||Heikkinen||Heikki < Henrik||17,935|
In 21st-century Finland, the use of surnames follows the German model. Every person is legally obliged to have a first and last name. At most, three first names are allowed. A Finnish married couple may adopt the surname that either spouse had as non-married, in which case this name will be the surname of their children. A spouse changing his or her name may decide to use a double-barrelled name consisting of his or her former and current official surname. In the case where both spouses keep their names they may choose either name for their children, but all siblings must share the same surname.  
All persons have the right to change their surname once without any specific reason. A surname that is un-Finnish, contrary to the usages of the Swedish or Finnish languages, or in use by any person resident in Finland cannot be accepted as the new name, unless valid family reasons or religious or national customs give a reason for waiving this requirement. However, persons may change their surname to any surname that has ever been used by their ancestors, if they can prove such claim. 
Surnames behave like regular words when forming grammatical cases. Thus, for example, the genitive of surname Mäki is Mäen, just like the regular word mäki ("hill") becomes mäen in the genitive. For given names this is not always the case even if the word is a regular word; for example Suvi ("summer") becomes Suvin in the genitive, not Suven.
In 1985, of the types of surnames, 38% of Finns had a -nen name, 8.9% -la, 7.4% with other derivative suffix (e.g., -io/-iö, as in Meriö, or -sto/-stö, as in Niinistö), 17.5% other names in Finnish, 14.8% non-Finnish (chiefly Swedish), 13.1% with compound word names (e.g., Kivimäki "stone hill", Rautakoski "iron rapids"). Only 0.3% had a double-barreled name (e.g., marriage of a Forsius to Harkimo giving Forsius-Harkimo). 
Patronymics were used in official documents until the late 19th century. Finns did not address each other by patronymics in colloquial speech. The natural Finnish way of referring to someone's parentage is the genitive: Matin Olli ("Matthew's Olaf") instead of the solemn Olli Matinpoika ("Olaf Matthew's son").  When patronymics were no longer required in documents, they quickly fell out of use.  They are still perfectly legal, but very rare, often representing a deliberate archaism. Unlike in Swedish, Finnish patronymics were not transferred into hereditary family names. Thus, the Finnish situation differs considerably from, for instance, Sweden, which has hundreds of thousands of Johanssons and Anderssons. The Swedish patronymics-like surnames are treated as any other surname. Real patronymics are handled like additional first names, i.e., one must still have a surname.  An exception is Icelandic citizens resident in Finland, who are allowed to follow the Icelandic name tradition.
The native Finnish tradition of first names was lost during the early Christian period, and by the 16th century, only Christian first names were accepted. The popular names were usually the names of saints whose cult was widespread. This resulted in some differences between the Western and Eastern Finnish first names, as the names in Eastern Finland might have had forms derived from Russian or Church-Slavic, instead of Swedish and Latin forms. For example, there are two Finnish cognates of George, Yrjö < Swedish Örjan and Jyri < Russian Юрий ( Yuri). The most important source for researching the name forms actually used by the Finns themselves in the 15th to 18th centuries are the surnames preserved in written sources, as these often are formed on the basis of a first name. The first names themselves are usually given in Swedish or Latin forms, as these are the languages used in the sources. The name actually used was a Fennicized form of the name, which might change as the person became older.  For example, a person given the Swedish name Gustaf in the parish register might be called Kustu as a child, Kusti as an adolescent, Kyösti or Köpi as an adult and Kustaa as an old man. 
In the early 19th century, almost all Finnish first names were taken from the official almanac, published by the Royal Academy of Turku, later the University of Helsinki. The names were mostly names of the saints whose cult had been popular before the Reformation, but the almanac also incorporated a number of names from the Old Testament and Swedish royalty, which were added to certain days during the 17th and 18th centuries.  During the 19th century, the Finnish forms were gradually added to the Finnish almanac, while the Swedish and Latin forms were removed (the Swedish forms were retained in a separate Swedish almanac). At the same time, the vicars gradually started to use Finnish name forms in parish registers. This in turn, cemented the Finnish name forms used.
Names with originally Finnish etymology were revived in the 19th century. In the absence of reliable information about ancient names, parents chose names of mythical characters from folklore ( Aino, Tapio), and many new names were created from Finnish words (Seppo "smith" or "skilled person", Ritva "birch twig"). Some clergymen initially refused to christen babies with such "pagan" names.  The first given name of Finnish origin, Aino, was accepted in the almanac in 1890, followed by numerous others in 1908. About 30% of Finns born in 1910–1939 received a name with Finnish etymology. 
By the 1930s, the use of Finnish names and name forms was stabilized and most of the popular names were noticed in the almanac. Since then, the almanac has been gradually changed to include new, popular names.  At present, all names which have at least 1,000 bearers are incorporated into the almanac of the University of Helsinki and given a "name day" ( Finnish: nimipäivä).  At present, 792 of the 35,000 first names used in Finland are listed in the Finnish almanac.  The nimipäivä calendar follows the Medieval Catholic Saint calendar when applicable.
First names are subject to changing fashions, while second or third given names are more traditional and typically trisyllabic. In the table below both first and middle names are counted. Since the digitalization of the Finnish national population database in the 1970s, the most popular names in Finland (of all Finnish residents or citizens who have lived after that point) have been  
|Men's names||Origin||Men named||Women's names||Origin||Women named|
|Juhani||Saint John||332,172||Maria||Virgin Mary||355,087|
|Johannes||Saint John||236,343||Helena||Saint Helen||166,254|
|Olavi||Saint Olaf||217,861||Anneli||new variant of Anna||143,411|
|Antero||Saint Andrew||180,783||Johanna||Joanna, also < Johannes||142,891|
|Tapani||Saint Stephen||152,220||Kaarina||Saint Catherine via Swedish Karin||129,888|
|Kalevi||Finnish mythology||141,428||Marjatta||Finnish mythology||122,602|
|Tapio||Finnish mythology||134,185||Anna||Saint Anna||111,180|
|Matti||Saint Matthew||126,720||Liisa||Saint Elisabeth||100,555|
|Ilmari||Finnish mythology||109,727||Annikki||Finnish mythology||96,836|
|Mikael||Archangel Michael||109,315||Hannele||new loan from German <Johanna||91,516|
Of the names listed, Annikki and Marjatta are etymologically related to Anna and Maria, but they are characters in the Kalevala, not used as given names before the 19th century.
At present, the Names Act ( Finnish: Nimilaki; Swedish: Namnlagen) of 1985 requires that all Finnish citizens and residents have at least one and at the most three first names. Persons who do not have a first name are obligated to adopt one when they are entered into the Finnish national population database. Parents of new-born children must name their child and inform the population registry within two months of the child's birth.  The name may be chosen freely, but it must not be
- a name used primarily by persons of the other sex
- a name foreign to the naming tradition in Finland
- a surname, except a patronymic as last given name
- a name already used by a sibling, if this is to be the only given name.
Waivers may be granted if valid family, religious or ethnic reasons give grounds to use a name contrary to these principles. Persons may change their first names once without a specific reason. For subsequent changes, valid reasons must be presented. 
As in general in European culture, the surname is seen as more formal and the first names as less formal. Strangers are expected to refer to each other by their surnames and using grammar in formal plural. The use of first names indicates familiarity, and children often refer to each other by first names only. However, in many workplaces familiarity between individuals working on the same site is assumed.
In contrast to other European tradition, the use of titles such as tohtori "Doctor" with surnames is not very common and is found only in highly formal contexts, or it is considered old-fashioned. The titles equivalent to Mr., Mrs. and Miss are herra, rouva and neiti, respectively. Thus, for example, in formal contexts, Matti Johannes Virtanen can be referred to as herra Virtanen or herra Matti Virtanen, if several Virtanens are present. In most other contexts, simply one name, surname or first name, is used. As in Swedish culture, politeness is often expressed by indirect address, such that the use of names might even be deliberately avoided.   In spite of this, formal Finnish features various titles, particularly presidential citations such as vuorineuvos or ministeri.
- E.g. Hormia, Y. (1941) Säätyläisnimiä Pyhämaan ja Pyhärannan rahvaan keskuudessa. Genos 12:13-17. (in Finnish). Retrieved 2015-10-13. (in Finnish)
- Antti Matikkala. Vapatietomuksesta ikonografiseen heraldiikkaan - vaakunoista, heraldiikasta ja niiden tutkimuksesta, in Henkilö- ja sukuvaakunat Suomessa, ed. Antti Vitikkala and Wilhelm Brummer.
- The whole section is based on the article Paikkala, S. Sukunimet sukututkimuksessa. Retrieved 11-6-2007. (in Finnish)
- Sukunimien muutokset Archived 2007-09-30 at the Wayback Machine.
- As of March 2012 [update], "Most common surnames", Finnish Population Register Center (English version), verkkopalvelu.vrk.fi/Nimipalvelu
- Equality in Finland. Information for Immigrants. Ministry of Labour. Page 2. Retrieved 3-11-2008.
- Nimilaki (694/1985) § 2, 7, 8a. Retrieved 8-3-2008. (in Finnish)
- The information here is taken from the Finnish Nimilaki (694/1985) (Name Act). Retrieved 11-6-2007
- Mikkonen, Pirjo; Paikkala, Sirkka. Sukunimet. Published in Joka kodin suuri nimikirja, Suuri Suomalainen Kirjakerho, Otava, Keuruu 1990. ISBN 951-643-476-2
- Paikkala(2004), page 542
- Paikkala(2004), pages 422-426, 543-544
- Nimilaki (694/1985) § 26. Retrieved 3-11-2008. (in Finnish)
- Sarilo, M. Nimien alkuperä. Campus. University of Tampere. Retrieved 3-11-2008. (in Finnish)
- Vilkuna (1976) page 15.
- Yleisimmät nimet. Retrieved 3-11-2008. (in Finnish)
- Vilkuna (1976), pages 19-20
- Kiviniemi (2006) pages 274-275
- Almanakkatoimisto. Kysymyksiä ja vastauksia. Retrieved 3-11-2008. (in Finnish)
- Nimipäivän vietto. Research Institute for the Languages of Finland. Retrieved 3-11-2008. (in Finnish)
- Nimipalvelu. Väestörekisterikeskus. Retrieved 3-11-2008. (in Finnish)
- The origins of the names are taken from Vilkuna (1976).
- Nimilaki (694/1985) §§ 1, 32a. Retrieved 3-11-2008. (in Finnish)
- Nimilaki (694/1985) § 32b. Retrieved 3-11-2008. (in Finnish)
- Meski, Arja. Miten viranomaiset puhuttelevat kansalaisia tiedotteissaan: ruotsin ja suomen viranomaistekstien vertailua. Stockholms universitet, 2008. http://su.diva-portal.org/smash/get/diva2:325726/FULLTEXT01 p. 37