Major James Hewitt (born 1958), former British cavalry officer, is famous for being the lover of Diana, Princess of Wales, and is widely reviled for his willingness to reveal details of their affair.

Diana admitted in her famous Panorama interview that she had committed adultery with Hewitt, saying, "Yes, I adored him. Yes, I was in love with him." Although it has been speculated that he is the natural father of Prince Harry, he reportedly met Diana for the first time in 1986, two years after Harry was born. Hewitt became Diana's riding instructor, with the affair beginning in 1987 and ending in 1992. He retired from the Life Guards in March 1994 after 17 years of service.

Hewitt made the news by attempting to sell letters that Diana had written to him. His reputation has been in a downward spiral ever since.