"Mad Men" Emmy Award-nominee Jon Hamm and his partner of 18 years, actress-filmmaker Jennifer Westfeldt, have announced they are ending their relationship.

"With great sadness, we have decided to separate, after 18 years of love and shared history," Hamm and Westfeldt told People magazine in a statement Monday. "We will continue to be supportive of each other in every way possible moving forward."

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Hamm, 44, and Westfeldt, who is in her mid-40s, fended off a tabloid's breakup rumors in April, with their representative saying at the time, "The story that appeared in this week's edition of In Touch magazine is not true. The only gentleman Jennifer visited regularly in Connecticut was Jon, while he was in rehab" -- a reference to the star's 30-day treatment for alcohol abuse, which his representative said he completed in March.

The couple met in 1997, and he appeared in her 2001 film "Kissing Jessica Stein," based on an off-off-Broadway play Westfeldt co-wrote and in which she played the title role.

In 2009, she and Hamm co-founded Points West Pictures, one of the production companies behind 2011's "Friends with Kids," which Westfeldt wrote and directed and in which they both starred.

The two, who have no children, were last seen publicly on July 22, People said, at the after-party for the New York premiere of the Netflix series "Wet Hot American Summer: First Day of Camp."

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In December, while being presented with the People Magazine Award for Television Performance of the Year -- Actor, Hamm honored Westfeldt in his acceptance speech saying, "There's another person who's actually sitting in the audience who basically told me when I wasn't working that I was still talented. And she's stuck with me for the last 16 years, even if the talent question remains up for grabs."