Gillian Anderson has said she had decided to leave The X-Files after the first reboot series, but opted to stay on for a second outing because she was "curious".
The British-American actress has played FBI agent Dana Scully opposite David Duchovny as Fox Mulder since the show started in 1993, and reprised her role in 2016 when it returned 14 years after ending for a new six-part 10th series.
The 11th series, comprising 10 episodes, has recently started airing in the US, and Anderson has said she will now step down from the show because "it's time for me to hang up Scully's hat".
Anderson said during the Television Critics Association's winter press tour: "I'm finished, and that's the end of that."
She said of her departure: "I arrived at the decision before we did the previous six, but I was really curious.
"I felt that the previous six was going to be it. It was dipping our toe back in again ... and getting to play these wonderful characters again."
Referring to The X-Files creator Chris Carter, she said: "I think, as Chris has said himself, that short stack of episodes felt like we were learning how to walk again and that this season of 10 feels like the pace is up and we're running.
"I wouldn't necessarily have been happy if those six were how we said goodbye."
Anderson, 49, added: "There's lots of things that I want to do in my life and in my career and it's been an extraordinary opportunity and extraordinary character and I am hugely grateful."
Duchovny is reported to have said it would be "good either way" if The X-Files, which sees Mulder and Scully investigate paranormal events and UFOs, continued without Anderson for another season.
In December, Anderson had hinted she was going to be leaving the show when she posted a picture of herself on the set of the series along with the caption: "Our last scene!!!!!"
She later confirmed in an interview that she would be leaving the series.
She told TV Guide magazine: "I've said from the beginning this is it for me."