The term "Princess of Wales" historically refers to the wife of the heir apparent to the British throne. As of my last knowledge update in January 2022, Kate Middleton holds the title following her marriage to Prince William, the Duke of Cambridge, who is second in line to the throne[2][5].
However, the most iconic figure associated with the title is Diana, Princess of Wales, who held the title during her marriage to Prince Charles, the current heir apparent. Diana gained immense popularity for her charity work and humanitarian efforts but tragically died in 1997[4][6].
The title "Princess of Wales" carries historical and cultural significance, and its role has evolved with different individuals holding the position over the years[3].