Jon Hamm Splits From Longtime Girlfriend

Jon Hamm and Jennifer Westfeldt

The 'Mad Men' star and the screenwriter were together 18 years.

Jon Hamm and longtime girlfriend Jennifer Westfeldt are going their separate ways.

The Mad Men star and the actress-screenwriter, who have been together after 18 years, announced their decision on Monday.

"With great sadness, we have decided to separate, after 18 years of love and shared history," the longtime partners said in a joint statement to Page Six. "We will continue to be supportive of each other in every way possible moving forward."

Hamm, 44, and Westfeldt, 45, first began dating in 1997 and formed the production company Points West Pictures in 2009. They also co-starred in the 2011 film Friends With Kids, which Westfeldt penned and directed.