"It was super fun today," Karlsson tells Viaplay.
Third place went to American Jessie Diggins, who was 6.2 seconds behind Karlsson at the finish line.
"So close, but I don't know what I could have done better today, so I'm happy. After all, Frida is a double Olympic champion, so it's not just anyone who is ahead," Linn Svahn tells Viaplay.
"Take a big bite"
Frida Karlsson also won Olympic gold in skiathlon and a silver with the Swedish relay team.
Svahn, second in Saturday's sprint in Lahti after Jonna Sundling, finished as the fifth skater in Finland and the Olympic sprint champion set the tone early in the race.
"It's a bit difficult when you start so early. I just tried to think about how I ski. It didn't feel like I was opening up that much, but I had to really bite the bullet between six and eight kilometers. Then I think it took its toll quite a bit," Svahn says.
There are both advantages and disadvantages to starting early in a race with an individual start, says Frida Karlsson.
"Today it was warm, so you could feel it getting looser and looser. At the same time, I have the times to go on, so it's going to be even," Karlsson says.
"Really fun"
After 8.4 kilometers, Karlsson passed Svahn and the 26-year-old, who won the mile race at the Olympics in freestyle, was finally just over four seconds ahead of her teammate at the finish line.
"It felt like home in training. It's fun to take up the fight anyway," Frida Karlsson says of battling teammate Svahn at the top.
"It's crazy. We have such a strong team. You celebrate a double victory even harder," she continues.
Jonna Sundling came in sixth (+19.1) and Moa Ilar seventh (+24.9). Maja Dahlqvist came in 18th (+51.2) and Moa Lundgren took 20th place (+52.5).
"A really good team performance," women's coach Stefan Thomson tells Viaplay.
Ebba Andersson skipped the competitions in Lahti and instead competed in the Ski Classics cross-country ski cup in Orsa on Saturday.
