After denying rumors of a rift earlier this year, Jon Hamm and Jennifer Westfeldt announced their split over Labor Day weekend, on Sept. 7, 2015.
RELATED: Jon Hamm's life in pictures
The couple released a statement to People: "With great sadness, we have decided to separate, after 18 years of love and shared history. We will continue to be supportive of each other in every way possible moving forward."
Back in March, Jennifer stood by the "Mad Men" star's side through a 30-day stay in rehab for issues with alcohol -- despite breakup buzz that had been swirling. And things seemed to be looking better between them after he got treatment.
"With the support of his longtime partner Jennifer Westfeldt, Jon Hamm recently completed treatment for his struggle with alcohol addiction," his rep explained in a statement released on March 24. They have asked for privacy and sensitivity going forward."
RELATED: Jon Hamm 'doing well' post rehab
But clearly, there was still trouble in paradise for Jon, 44, and Jennifer, 45.
The now-exes met back in 1997 and were in a committed relationship for 18 years though they never wed.
RELATED: Shocking celeb splits
Back in 2010 Jon spoke about their unique bond with Pardade: "I don't have the marriage chip, and neither of us have the greatest examples of marriage in our families. But Jen is the love of my life, and we've already been together four times longer than my parents were married."
- Jan. 17, 2018 These girl groups mastered matching outfits!