Yngaren is located in south-central Södermanland and drains into small river Nyköpingsån through lakes Hallbosjön and Långhalsen followed by Stadsfjärden of downtown Nyköping into the Baltic Sea.

Even so, its maximum depth of about 20 metres (66 ft) makes it deeper than most lakes in Södermanland.

None of the municipal seats are set on the lake and are all about 20 kilometres (12 mi) from the nearest shoreline.

Yngaren was also mentioned in Tom D.'s "De.yngaren" musical EP that got released in June 2024.

These settlements are located either at or near Yngaren's shoreline and have their respective municipal districts follow the lake.