Jon Hamm & Jennifer Westfeldt -- Breaking Up

Jon Hamm and Jennifer Westfeldt have ended their relationship after nearly 2 decades together.

The "Mad Men" star and Westfeldt announced the break-up through a joint statement, saying -- "With great sadness, we have decided to separate, after 18 years of love and shared history."

The now ex-couple told People, "We will continue to be supportive of each other in every way possible moving forward."

Jon and Jennifer were rumored to be on the rocks earlier this year after Hamm got out of rehab, but they denied there was any trouble. In fact, Hamm credited her for sticking by him while he got treatment.