Monaco's Prince Albert to have heir

Monaco's Princess Charlene and Prince Albert II are expecting their first child at the end of the year.

Monaco's Prince Albert II and his wife Princess Charlene are expecting their first child together. (AAP)

Princess Charlene, the South African wife of Monaco monarch Prince Albert II, is expecting the couple's first child at the end of the year, the royal palace has announced.

"Prince Albert and Princess Charlene have the immense joy to announce they are expecting a happy event," the palace said in a statement.

"The birth is due at the end of the year."

Charlene, 36, is a former Olympic swimmer who married Albert in 2011.

The new baby, who will replace Albert's sister Caroline as the next in line to the Monaco throne, will be Charlene's first child.

Albert already has two recognised children, US-born daughter Jazmin, who is now 22, and a younger son, Alexandre, from his relationship with an Air France hostess of Togolese origin.