Prince of Beira (Portuguese: Príncipe da Beira, feminine: Princesa da Beira) is a title traditionally granted to the heir apparent to the throne of Portugal. The title's original use that it be granted on the eldest daughter of the reigning monarch of Portugal. Tied with the title of Prince of Beira, is Duke of Barcelos, as heir to the Duke of Braganza and Prince of Brazil (later Prince Royal of Portugal). The title's name has its origins in the Beira province in central Portugal.

The title was presumably created (no records of its earlier existence or grants) by King John IV of Portugal, the new monarch, first of the Braganza dynasty, sometime in the 1640s. It was firstly given to his eldest surviving daughter, Infanta Joanna of Portugal, 1st Princess of Beira. It was the King's intention that the male heir apparent would be Prince of Brazil and later also Duke of Braganza, whereas Princess of Beira was originally quite similar to that of French Madame Royale or the British Princess Royal. The title had no original connection to being one for next heirs of the throne - King John IV had a second son, and soon a third, but the daughter kept Beira and the boys received dukedoms (Braganza and Beja). However, Joanna died young in 1653.

Afterwards, the title kept being granted and regranted several times during the remaining Portuguese monarchy. However, the precedent of being granted to the monarch's eldest daughter in a situation where he had several living sons, was repeated sometimes in later centuries.

The title's first connection with the position of the heir was from 1669 onwards, when it was held by the Infanta Isabel Luísa, Princess of Beira (1669–90), the only then living child of King Peter II. She received it as the eldest daughter of the king, but as she also was the heiress presumptive until 1688, a new tradition got its groundwork.

According to the first tradition, the next holder would be Infanta Barbara of Portugal (1711–58), the eldest daughter of King John V of Portugal. In 1729, she wedded Infante Fernando of Spain, the Prince of Asturias.

Then, on December 17, 1734 the title was created anew by King John V of Portugal, in favour of his newborn eldest granddaughter Infanta Maria Francisca. She was the eldest daughter of the heir-apparent of the monarch. This was the first time when it was granted two generations down from the monarch. As the future Joseph I (the then Prince of Brazil) was to remain without sons, the new Princess of Beira would later become the proclaimed heiress and ultimately to ascend the throne.

In 1750 the newly ascended King Joseph I (believing that no sons would be forthcoming--indeed, his wife and he produced no further issue after 1746, as is known in hindsight) proclaimed his eldest daughter the official heiress and granted her the "crown-princely" title Princess of Brazil (but apparently not that Duke of Braganza). He in 1761 further granted Maria's eldest son, Infante Dom José Francisco (1761–88), the title Prince of Beira. For the first time, the title was held by a male.

This created a new tradition. The situation now, effectively, was that the king's official heir held the Princedom of Brazil, and Prince of Beira was Brazil's heir-apparent. The situation had been the same (though unintentionally) during 1734-50, when the monarch's heir-apparent was Prince of Brazil, and Brazil's obvious heir was Princess of Beira. This was to be repeated after that time, as monarchs granted Beira to the second heir-apparent whenever possible.