Prince Bertil of Sweden, Duke of Halland (Bertil Gustaf Oskar Carl Eugén; 28 February 1912 – 5 January 1997), was a member of the Swedish royal family. He was the third son of King Gustaf VI Adolf and his first wife, Princess Margaret of Connaught, as well as the uncle of King Carl XVI Gustaf. From 1973 to 1979, he was heir presumptive to his nephew Carl XVI Gustaf and the Swedish throne.

Bertil was born on 28 February 1912 at Stockholm, as the fourth of five children born to Princess Margaret of Connaught and Crown Prince Gustaf Adolf of Sweden. His siblings included: Prince Gustaf Adolf, Duke of Vasterbotten, Prince Sigvard, Duke of Uppland, Princess Ingrid and Prince Carl Johan, Duke of Dalarna.

The family lived in apartments at Stockholm Palace in Stockholm, at Ulriksdal Palace near the capital in Ulriksdal and at the summer residence: Sofiero Palace in Helsingborg in the southernmost province of Sweden, Scania.

Bertil was granted a very old dukedom, one that was bestowed in the Middle Ages on various Danish and Swedish royal relatives. After his eldest brother, Prince Gustaf Adolf, died in 1947, leaving an infant son, Prince Carl Gustaf, in the line of succession, and because his elder brother Sigvard had already given up his place in the succession (owing to a constitutionally unacceptable marriage), it seemed likely that Bertil could one day become regent. After Carl Gustaf became king, Bertil remained the next in line to the throne (until the birth of Prince Carl Philip in 1979), and continued to act as the King's deputy.

When the Act of Succession was changed in 1980, rights to the throne were restricted to Carl XVI Gustaf and his descendants; however, a special addendum was made for Bertil's case, so that he became third (and, after the birth of Princess Madeleine in 1982, fourth) in line to the throne.

Bertil became a naval officer; and, during the Second World War, he served as Swedish naval attaché at the embassy in London.

In 1943, Bertil met his long-term partner, Welsh commoner Lilian Craig. However, in order to preserve his place in the royal succession, Bertil and Lilian did not marry for decades. They lived together discreetly, as a fully private arrangement, from the 1940s until their marriage was announced and took place in 1976. Their common base was a home in Sainte-Maxime, in the south of France.

Since his life with Craig was not official, Prince Bertil's single status meant he was suggested as a match for, among others, Princess Margaret of the United Kingdom. After the death of Gustaf VI Adolf in 1973, the new king, Carl XVI Gustaf, married a non-royal woman and approved the marriage of Bertil and Lilian, which took place at Drottningholm Palace on 7 December 1976.^{[citation needed]}