Carey Mulligan was born and raised in London, England.
Almost everything regarding Mulligan's religion comes from secondary sources. Nothing straight from her. However, there's good reason to believe she's a Catholic. Her name, Mulligan, is of Irish origin and her great-grandfather emigrated from Ireland to England. Plus, she attended an all-girls Catholic school in her formative years.
The fact that she doesn't talk about it might indicate that she's not all that religious–or it could be a topic she prefers to keep to herself. One site claims that she's of the "spiritual, not religious" variety and that her Catholic schooling caused her to feel that Catholicism is too strict a religion. I'd be inclined to believe it.
Whatever the case may be, Mulligan has married into a very religious, though Evangelical Christian, family. Mulligan met Marcus Mumford, of Mumford & Sons, as a pen pal through their respective churches as children. They married in 2012 with Mumford's father, a vicar with the Vineyards Church, officiating the wedding. In fact, Mumford's father founded the Vineyards Church. So you know Mulligan's going to get a healthy dose of religion, whether she likes it or not.
Politics and old age
Mulligan is equally quiet about her political views as she is about her religious views. One of her pet issues, however, is Alzheimer's Disease. Her grandmother is afflicted with the disease and it's inspired Mulligan to represent the Alzheimer's Society and help raise awareness.
This led to her only political moment that I've been able to find. Mulligan met with British Prime Minister, David Cameron, to discuss political options to heightening awareness and battling Alzheimer's.
Beyond that, Mulligan's celebrity has got her on the guest list at a White House state dinner. So, she's hobnobbed with the likes of Obama, but not in any political capacity.
Perhaps as Mulligan grows older or has children or Britain legalizes gay marriage, she'll be inclined to comment more on political issues. Keep us posted in the comments.