What did actress Grace Kelly change her surname to in 1956?

Grace Patricia Kelly (November 12, 1929 – September 14, 1982) was an American actress who, after marrying Prince Rainier III in April 1956, became HRH Princess of Monaco.

The Oscar-winning actress Grace Kelly retired from acting at the age of 26 to marry Rainier III (Rainier Louis Henri Maxence Bertrand Grimaldi) in 1956 and began her duties as Princess of Monaco. The ceremonies in Monaco were on 18 April 1956 (civil) and 19 April 1956 (religious). They had three children: Caroline, Albert and Stéphanie. She retained her American roots, maintaining dual U.S. and Monégasque citizenship. She died on September 14, 1982, a day after suffering a stroke while driving, causing her car to crash.