D. Isabel, Princess Royal of Portugal, Duchess of Braganza (born 22 November 1966), is a Portuguese businesswoman, noblewoman, and the wife of Duarte Pio, Duke of Braganza, the current pretender to the defunct Portuguese throne. Born to descendants of Portuguese peerage , Castro Curvelo de Heredia worked as an assets manager prior to her marriage. Since becoming the Duchess of Braganza, Isabel has left the professional world, devoted her attention to her family, and become patron to several Portuguese charities and non-profit foundations. She and the Duke have had three children together, thus securing the continuation of the House of Braganza.

Isabel Inês Castro Curvelo de Herédia was born on 22 November 1966, in Lisbon, to D. Jorge de Heredia, an architect, and Dª Raquel Leonor Pinheiro de Castro Curvelo, his wife. Since birth, she was entitled to the honorific styling of Dona (Lady), being a descendant in the male lineage of Francisco Correia de Herédia, 1st Viscount of Ribeira Brava, of Portuguese peerage and a famed republican, who was involved in the failed republican uprising of 28 January 1908.

Castro Curvelo de Heredia lived between metropolitan Portugal and Portuguese Angola until 1975, when Angola was granted independence. Her family subsequently moved to São Paulo, Brazil. There, she studied at the Colégio São Luís, a Jesuit-run institution. In 1990, she obtained a degree in business administration from the Fundação Getúlio Vargas and returned to Portugal to a job in BMF — Sociedade de Gestão de Patrimónios, S.A. She specialized as an asset manager.

On 13 May 1995 she married Duarte Pio, Duke of Braganza, at Jerónimos Monastery. Present at the ceremony were representatives of various European royal and noble houses, President of the Republic Mário Soares, Prime Minister Aníbal Cavaco Silva, and President of the Assembly António Barbosa de Melo, among others.

Following her marriage and the birth of her first child, Afonso, Prince of Beira, the Duchess of Braganza resigned from her professional life and devoted herself to the management of her family and the patronage of various causes. Using her privileged position for the good of others, Isabel has become the patron to:

Refúgio Aboim Ascensão – Faro: A private social solidarity institution which helps victims of physical abuse, negligence, and any other social injustice or disadvantage adapt socially.
Ajuda ao Recém Nascido: An institution linked with the Alfredo da Costa Maternity, in Lisbon, which provides clothes, provisions, and other necessities children recently born to disadvantaged families.
Trissomia 21: A private social non-profit association which sponsors and supports research and education for Down syndrome.
Associação Portuguesa de Miastenia Grave e Doenças Neuro-Musculares: An association linked with Santa Maria Hospital, in Lisbon, which works for the improvement of patient care at the hospital.
Ajuda de Berço: An institution which temporarily hosts children, from new-borns to three-year-olds, that are in situations where their parents cannot take care of them.
Os Francisquinhos: A social solidarity association linked with São Francisco Xavier Hospital, in Lisbon, that collaborates with parents and friends of deformed children, children born with serious diseases, and children born with complications due to the toxic dependencies of their mothers.