28-year-old Sarah Sjöström improved her time from 24.50 in the trials to 24.26 in the semi-finals.
That made her the fastest of all.
One tenth ahead of runner-up Katazyna Wasick, who will be Sjöström's biggest competitor for the gold.
- Every time I've swum this year, I'm around 24 low.
I went under 24 seconds at the WC, and hope I can do it tomorrow too.
As I've shown so far this year, I've gotten better every race.
Going for the second gold in the EC
The final will be Sjöström's second individual in this championship.
In the 50 meter butterfly, she won in superior style.
- Swimming is so technical.
You can go one hundred percent, but if the technique is not one hundred percent, it doesn't matter how hard you go.
I try to swim as fast as my technique allows.
SVT's expert Lars Frölander about the race:
- Her swimming was a little more determined than in the trials, but still controlled, he says.
Missed the final - but broke a personal record
For Sara Junevik, there was no final place in the sprint distance.
The Swede, who is more focused on the 50 meter butterfly, swam in a time of 25.35, which was a new personal record by one hundredth.
It was also clearly faster than the attempt where she had a time of 25.63.
- I got away much better now, a better race.
Although I know I can do even better.
How far down can you go?
- I did 25.3 in training before we left, so it's somewhere you want to be, says Junevik to SVT Sport.