Danes's rep, Jodi Gottlieb, confirms the actress is expecting her first child with husband Hugh Dancy.
The news was first reported on People.com.
Thirty-three-year-old Danes and 37-year-old Dancy met on the set of the film Evening and were married in 2009 in France.
The actress first became famous as a teenager on the television drama My So Called Life, where she won a Golden Globe Award and was nominated for an Emmy. The show was cancelled after its first season but developed a cult following.
Dancy will star in the upcoming US TV series Hannibal, adapted from the novel Red Dragon by Thomas Harris