Katarina-Sofia was a so called borough (stadsdelsområde) in central

Stockholm City Centre

Stockholm City Centre is the city centre of Stockholm in Sweden. The entire city of Stockholm is also the centre of the Stockholm Metropolitan Area....

 Stockholm

Stockholm

Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...

, named after the two parish

Parish

A parish is a territorial unit historically under the pastoral care and clerical jurisdiction of one parish priest, who might be assisted in his pastoral duties by a curate or curates - also priests but not the parish priest - from a more or less central parish church with its associated organization...

es of Katarina

Katarina kyrka

Katarina kyrka is one of the major churches in central Stockholm, Sweden. The original building was constructed 1656–1695. It has been rebuilt twice after being destroyed by fires, the second time during the 1990s...

 and Sofia

Sofia kyrka

Sofia kyrka is one of the major churches in Stockholm, Sweden. It was designed during an architectural contest in 1899, and was inaugurated in 1906. Sofia church belongs to Sofia parish of the Church of Sweden.-See also:* Katarina kyrka* Maria Magdalena Church...

. Effective January 1, 2007, the borough merged with the borough of Maria-Gamla Stan

Maria-Gamla Stan borough

Maria-Gamla Stan was a so called borough in central Stockholm until January 1, 2007, named after the Maria parish and the Stockholm Old Town in the borough....

 to form the Södermalm borough

Södermalm borough

Södermalm is a city district area in central Stockholm, created January 1, 2007, through the merging of the boroughs of Maria-Gamla Stan and Katarina-Sofia. It covers the island of Södermalm and some neighboring districts.-Overview:...

.

Katarina-Sofia was made up of the eastern half of Södermalm

Södermalm

Södermalm, often shortened to "Söder", is a district in central Stockholm. It covers the large island formerly called "Åsön". With a population of 99,685, it is one of the most densely populated districts of Scandinavia...

 and Hammarby Sjöstad

Hammarby Sjöstad

Hammarby Sjöstad is a part of Stockholm municipality, currently undergoing major urban redevelopment. It is located on both side of lake Hammarby sjö, bordering Nacka Municipality to the east...

 (Södra Hammarbyhamnen). The population was 42,750 on an area of 3.36 km², which gave a density of 12,723.21/km².