The couple confirmed the news via their rep on Tuesday.
"After much thought and careful consideration, we have made the difficult decision to divorce following our separation last summer," the statement reads. "We have the utmost respect for each other and remain close friends."
The pair married in January 2018 and Portner, a 26-year-old dancer, supported Page, 33, when he came out as transgender in December.
"I am so proud of @elliotpage. Trans, queer and non-binary people are a gift to this world. I also ask for patience & privacy but that you join me in the fervent support of trans life every single day. Elliot’s existence is a gift in and of itself. Shine on sweet E. Love you so much," Portner posted at the time.
While Page's statement at the time read, "Hi friends, I want to share with you that I am trans, my pronouns are he/they and my name is Elliot. I feel lucky to be writing this. To be here. To have arrived at this place in my life."
Page -- of "Juno" and "Umbrella Academy" fame -- also reflected on his gratefulness for the support he has received while embarking on this new chapter.
"I feel overwhelming gratitude for the incredible people who have supported me along this journey. I can't begin to express how remarkable it finally feels to finally love who I am enough to pursue my authentic self," Page stated.
He added, "I've been endlessly inspired by so many in the trans community. Thank you for your courage, your generosity, and ceaselessly working to make this world a more inclusive and compassionate place. I will offer whatever support I can and continue to strive for a more loving and equal society."
Page publicly came out as gay at a conference in Las Vegas for educators and counselors who work with gay youth in 2014.
Fox News' Melissa Roberto contributed to this report.