The 27-year-old came to the independent cinema showcase Monday to announce that she will produce and star in a film called "Inconceivable," set to start shooting in March.
She was joined by producer and financier Randall Emmett, who called Lohan "one of the greatest young actresses of her generation."
Lohan said she is grateful to be at Sundance and back in the movie business.
"I've never had the honor of coming here before ... to bring something to the table, which is starting fresh for me," said Lohan, smiling broadly. "And I'm filming my Oprah docu-series right now, so I get to show that to the people who have been watching that as well.
"It's a nice change to be back among people that are in the industry that I've been in since I was a kid."
A crew from the OWN series filmed Lohan's announcement at Monday's news conference, where reporters were told that if they asked personal questions, they would be escorted out.
Emmett said Lohan found the script and insisted they make it together.
"She read the script, she called, she said, 'We're making this movie, are you in or out?'" he recalled. "I said, 'I'm in.'"
Lohan will also help select the director and cast the film, he said, adding that he expects a director to be announced next week.
She described the film as a psychological thriller about a woman trying to reclaim something she lost, adding that she "related to the character in a lot of ways."
Emmett said moviegoers "are going to really be shocked when they see Lindsay take this role on." Lionsgate will release the film, he said.
Though Lohan served as an executive producer on her 2013 film "The Canyons," her role is even larger this time around.
"It's therapeutic for me to throw myself into something that really excites me and something that I love to do so much," she said. "There's nothing better than having seen all of your ideas and thoughts that you've been thinking about to come to fruition and to share that with people. I think that's why I've always loved making movies so much. So it's nice to be able to have another position in the film rather than just showing up and being on the set."
No director or co-stars have been announced, but Lohan already has plenty of ideas.
"I even approached Juliette Lewis and was emailing some other people," she said.
And she has a dream co-star: "I don't know if she would do it, but I would die if she did: Jessica Lange."