Her official title will be Her Royal Highness Princess Charlotte of Cambridge.
The baby girl was born in the Lindo Wing of St. Mary's Hospital, the same place where Kate, 33, gave birth to the couple's first child, Prince George, in July 2013. The new baby is now fourth in line to the throne behind Prince Charles, William and George.
The naming of the second royal baby is similar in time frame to when the Duke and Duchess of Cambridge chose George Alexander Louis for their first child. George was born on July 22 and his name was released a little more than a day later.
Prince William's full name is William Arthur Philip Louis. When William was born on June 21, 1982, his parents didn't reveal his name until one week later. William's father, Prince Charles, was a month old before his name was made public.
William's brother, Harry, has been an exception. His name was announced on the day he was born.