The Oldenburg City Archive is responsible for archiving written documents or other information media related to the City of Oldenburg.

The basis of this work is the Lower Saxony Archive Act of 1993, which also obliges the local authorities to safeguard their archives in the long term. Documents in the sense of the Act are "files which are either written or saved on machine-readable data media with attachments, certificates and other individual papers, maps, plans, drawings, sketches and posters, as well as seals and stamps, image, film and sound recordings, card index files as well as electronically saved files and microfiches, including the regulations and processes to evaluate the documents."

In all the total volume of the City Archive – measured in running metres – extends over a distance of more than 1.4 kilometres.

The history of the City Archive is described in the publication "100 Jahre Stadtarchiv Oldenburg 1903 – 2003" (100 years of the Oldenburg City Archive), published by the City Archive in Oldenburg in 2004, Volume 6.