Sigvard Oscar Fredrik Bernadotte, (7 June 1907 – 4 February 2002) born as, and until 1934 known as, Prince Sigvard of Sweden, Duke of Uppland, was a member of the Swedish Royal Family and a successful industrial designer by profession.
He was the second son of the future King Gustaf VI Adolf and his first wife, Princess Margaret of Connaught, eldest daughter of Prince Arthur, Duke of Connaught and Strathearn and granddaughter of Britain's Queen Victoria. He was a Prince of Sweden from birth, but was excluded from the line of succession in 1934 when he married a woman of unequal rank, a violation of provisions prohibiting marriages between a Prince and a "private man's daughter" (Swedish: enskild mans dotter), in force at the time, contained in both the 1809 Instrument of Government and the 1810 Act of Succession, and, in addition, he lost his princely and ducal titles as decided by the King in Council. As per the king's wishes he was then to be called only Mr. Sigvard Bernadotte in Sweden. In 1951 he was granted Luxembourgian titles of nobility, the interpretation of which remained a point of contention with the Royal Court for the rest of his life, Bernadotte having formally declared in 1983 that his title was Prince Sigvard Bernadotte.
He was a paternal uncle of King Carl XVI Gustaf of Sweden and a maternal uncle of Queen Margrethe II of Denmark and Queen Anne-Marie of Greece.