Nyköping is a locality and the seat of Nyköping Municipality, Södermanland County, Sweden. The city is also the capital of Södermanland County.Nyköping includes Arnö on the southern shore of the bay just a couple of kilometres from the city centre, and it forms a wider conurbation with the neighbouring minor municipality and town of Oxelösund 10 kilometres south of its outskirts.
Nyköping has a population of over 32,759 people. Nyköping also forms part of the wider Nyköping area which has a population of over 36,000 people.
Nyköping is Twinned with: Iisalmi, Finland • Lauf an der Pegnitz, Germany • Notodden, Norway • Nykøbing Falster, Denmark • Salacgrīva, Latvia • Vyborg, Russia • Kangaroo Point, Australia • Ōarai, Japan.