Prince Harry, the youngest son of Prince Charles, Britain's heir to the throne, marries American actress Meghan Markle in a lavish ceremony at the 15th Century St George's Chapel in Windsor Castle.
Guests have already started arriving for the glittering event which is expected to draw audiences from across the world.
The official ceremony begins at 11 am GMT (1 pm South African time) but the proceedings before and after the wedding ceremony will keep viewers glued to their screens.
More than 100 000 spectators are expected to line the streets around the castle which has hosted numerous royal weddings over the centuries.
This royal wedding is unusual in that Meghan, 36, is a celebrity in her own right. Harry, 33, is sixth in line to the British throne.