Returning to the pool eight months ago after having her first child, the 32-year-old took gold in a time of 25.05 seconds, beating Belgium's Roos Vanotterdijk (25.12) and fellow Swede, Sara Junevik, who secured bronze with a 25.51 race.
The gold and bronze are Sweden's first medals in Paris across all sports at these championships. Unsurprisingly, the Swedes could rely on Sjostrom, who won her 18th European title overall, 18 years on from her first European Championships in Rome as a 14-year-old.
The holder of the 50m butterfly world record and three-time Olympic champion now has 99 major international medals, but in her mind, this one was never guaranteed: "It was great fun. It wasn't something I took for granted when I started the season," she told the media after the race.
However, the competition only seemed to be going one way, as Sjostrom was the fastest in the heats and in the semi-finals, registering 25.40 and 25.12 before saving her fastest time for the final.
For Junevik, it's a fourth European medal in total, and a second in the 50m butterfly after the gold she won in Belgrade in 2022.