In Swedish, the province name is frequently shortened to Sörmland.
Södermanland means "Southern men's land". It was used as a directional reference to lake Mälaren, compared to Uppland (north) and Västmanland (west).
The terrain is flat, with its highest altitude being Skogsbyås at 124 meters elevation. The terrain largely consists of water filled hollows covered with woods on the heights.
There are three major water regions. One in the west, where lake Hjälmaren drains into Mälaren. There is a second water region on Södertörn, which is rather small in size and has no larger lakes: Bornsjön 6.5 km², Orlången 2.5 km², Magelungen 2.9 km². The third is to the south towards Kolmården.
The population of Södermanland is 1,104,611 as of 2004. It distributes over four counties as follows:
|part of Stockholm County||837,052|
|part of Västmanland County||6,743|
|part of Östergötland County||436|
The earliest recorded history is generally of the legendary kind. Before the 7th century it is deemed to have been governed by petty kingdoms. This period ended when Ingjald the Ill-Ruler allegedly had a number of local rulers arsoned around 640.
The oldest city with the historical city status in Södermanland was Södertälje, a privilege granted around 1000. Nyköping received the privilege in 1187. In the 13th century, Stockholm was granted the privilege; in the 14th century followed by Strängnäs, Torshälla and Trosa.
Around 1100, Strängnäs became the episcopal seat with a bishop and cathedral. It was for a long time the only diocese of the province. In 1942 the Diocese of Stockholm was established, claiming parts of the Strängnäs territory.
The first affirmative records date from the 13th century. King Magnus Ladulås was given the province in 1266, and settled himself on the manor at Nyköping. Nyköping became one of the most important cities in Sweden. In 1317, Nyköping become the location of the infamous Nyköping Banquet where King Birger had both his brothers murdered to take possession of the crown and avenge earlier wrong-deeds.
In 1523 the King Gustav Vasa, referred to as the Sweden's father of a nation, was crowned in Strängnäs. The date, June 6, eventually is commemorated as the national holiday. Karl IX, a son of Gustav Vasa, favoured the province, fortifying castles and establishing early industries.