Sjöström took gold in the 50m butterfly in a time of 24,58 seconds. Her success followed on from taking a silver medal in the 100m Freestyle event.
A delighted Sjöström told SVT News. "It was so nice. It was in the semi-final where I did not succeed, everything was bad. In the final, I managed all the details. It was really nice. I was so tired after the 100 freestyle, I fell down twice afterwards. My coach went looking for me in the hallways, I could barely walk. It was really tough."
The five-day championships runs until Sunday, 7 December.