A spokesman for Catherine said: "Catherine and Michael are taking some time apart to evaluate and work on their marriage."
Michael, 68, was diagnosed with throat cancer in 2010 while Welsh actress Catherine has suffered with bipolar II disorder for some time.
The Behind The Candelabra star underwent six months of chemotherapy and radiotherapy before being given the all clear in January 2011.
Shortly afterwards, Catherine checked herself into a psychiatric hospital in Connecticut suffering from bipolar II disorder, which causes cycles of high and low moods often with periods of depression.
It is believed that the condition was brought on by the stress of dealing with her husband’s illness. She received treatment again for the disorder earlier this summer.
The Hollywood power couple haven't been photographed together since a Manhattan gala in April, attending events solo and holidaying separately with their children Dylan, 13, and ten-year-old Carys.
They are said to have made the decision to "take a break" in May after Michael returned from this year’s Cannes Film Festival, but they chose to make the official announcement just this week.
At Cannes, Michael bravely spoke about his recent battle with cancer as he discussed his first acting role since beating the disease.
The highly-respected actor broke down at the esteemed film festival press conference for his latest film, Behind the Candelabra, in which he plays the flamboyant late musician Liberace.
"For me this has a… sorry," Michael said, his voice full of emotion, as he started to cry. "Because it was right after my cancer. And this is a beautiful gift. I am eternally grateful." His words were met with applause.