He was born around 1440, the son of Gustav Anundsson of the Sture family and Birgitta Stensdotter Bielke, half-sister of the future Charles VIII.

Sture fought with Bishop and Regent Kettil Karlsson Vasa during the uprising against the Danish King Christian I in 1464, taking part in the decisive victory at Haraker.

He served as a military commander under King Charles VIII, defeating Erik Karlsson Vasa's uprising at Uppbo in 1470 and later in the same year successfully beating back Christian I's forces at Öresten.

He married Ingeborg Tott, niece by marriage of Magdalen of Sweden, in 1467; she was a renaissance personality interested in theology and science and seems to have had some importance in the intellectual development during his reign.

On the death of King Charles on 15 May 1470, Sture immediately became the most powerful noble and political force in the country and was elected Lord Protector and Regent of Sweden (riksföreståndare) by the Riksmöte in Arboga on 1 May 1471.

The sculpture Saint George and the Dragon in Storkyrkan in Stockholm, commonly attributed to the German sculptor Bernt Notke, was raised to commemorate the battle.

In 1487, Sture fought a successful war against the powerful Tott dynasty, forcing them to cede Öland and Borgholm to Sweden, while Denmark received Gotland.

In 1493, the Danish and Norwegian king, Hans (also called John I), formed an alliance with Ivan III of Russia against Sten Sture.

Sture had no legitimate children from his marriage with Ingeborg Tott, only a daughter born out of wedlock, Birgitta, who became a nun in Vadstena Abbey.

However, Erik Johansson was described by his contemporaries as a simpleminded and brutal man, prone to violent outbursts and on more than one occasion charged with manslaughter, and lacked the political skill of his uncle Sten Sture.

To commemorate the victory at Brunkeberg, Sten Sture ordered a wooden monument for Storkyrkan in Stockholm, Saint George and the Dragon, built in the late 1480s.