Though they lived together for many years, Hamm, 44, and Westfeldt, 45, never married and chose not to have kids.
PHOTOS: Mad Men stars off screen “I have a tremendous amount of respect for my friends who do balance this particular career with raising a kid, 'cause it's a tricky environment to bring them into...
"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," Hamm and Westfeldt said in a statement shared with Us Weekly.
During 2000, he made his feature movie debut in the space adventure movie Space Cowboys.
His performance earned him the Golden Globe Award for Best Actor in a Television Series – Drama during 20 and the Primetime Emmy Award for Outstanding Lead Actor in a Drama Series during 2015. During 2008, Hamm appeared in a remake of the science fiction movie The Day The Earth Stood Still.It cemented Basinger and Rourke’s place as sex symbols for a time.It also opened up audiences to the idea of high profile erotic films like Gus Van Sant’s film was not the first to include sex scenes between two men, but its casting of high profile heartthrobs like Keanu Reeves and River Phoenix as street hustlers in a homosexual relationship was pretty major.The film explored risqué themes of sexual dominance and shows some fairly kinky scenes.It also has a memorable scene involving a refrigerator.