What title is given to the spouse of the heir apparent?

The title given to the spouse of the heir apparent is "Princess of Wales." This title is traditionally conferred upon the wife of the Prince of Wales, who is the heir apparent to the British throne. The title carries significant historical importance and recognition, as it has been used by many royal figures over the years, including notable princesses.

In the context of British royalty, being named Princess of Wales highlights the close association with the heir apparent and symbolizes a role that is often involved in charitable activities and public engagements. The title also has roots that connect it to Welsh heritage, as it was established in the context of the historical relationship between England and Wales.

Other titles listed, like Duchess of Cambridge or Duchess of Edinburgh, are titles that signify different roles or positions within the royal family but are not directly related to the spouse of the heir apparent. Queen Consort refers to the wife of a reigning king, which again does not apply in this situation since the question specifically asks for the spouse of the heir apparent.