The name is a Russian diminutive form of Ekaterina and spun off as a well-established independent given name across Western Europe. In Russian, this is the equivalent of Katie.
In France, Katia appeared among the Top 100 most popular female names between 1968 and 1979. Katia peaked at #42 in 1970. As of 2018, the name has not been in the French Top 1000 since 2004. Likewise, in Italy, it appeared in the Top 200 Most Popular Female Names between 1999 and 2007 and peaked at #141 in 1999. While in the United States, Katia appeared in the Top 1000 between 1996 and 2001 and peaked in 1996 at #772.
In the 1980s, Katja became extremely popular in Northern Europe, especially in Germany and Scandinavian countries.
In English, the name is sometime transliterated as Katya.
Its latinate form of Catia is occassionally used in Italy, Romania, Portuguese-Speaking and Spanish-speaking countries. Cátia and Kátia is used in Brazil.
As an independent given name, it is seldom used in Russia.
Countries/Languages in which Katia is in use: Bulgarian, Danish, English, French, German, Greek, Hungarian, Italian, Norwegian, Romanian, Portuguese, Spanish, Swedish.
Countries/Languages in which Katja is in use: Bosnian, Croatian, Danish, Dutch, Estonian, Finnish, German, Latvian, Macedonian, Norwegian, Serbian, Slovenian, Swedish