According to royal officials, the couple will marry on April 29 in Westminster Abbey, the historic London church where Princess Diana's funeral was held.
William and Middleton chose the date because they wanted a spring wedding.
The palace said the royal family and the Middletons will cover the cost of the nuptials, apart from security.
April 29 is also the feast day of St. Catherine of Siena, whose name Middleton shares - though that is a coincidence. The government said the day, a Friday, would be a public holiday.
Prince William's private secretary, Jamie Lowther-Pinkerton, said the couple chose the 1,000-year-old abbey in central London because despite its size - it holds 2,200 people - it has a sense of intimacy.
"Even at the altar, it seems like a parish church," he said.
William's grandmother, Queen Elizabeth II, and her mother both married at the abbey, where British kings and queens are also crowned.
William and Kate decided against celebrating their nuptials at St. Paul's Cathedral, where William's parents married in 1981.
The Associated Press contributed to this story.
