Infanta Margarita Teresa in a Blue Dress is one of the best-known portraits by Spanish painter Diego Velázquez. Executed in oil on canvas, it measures 127 cm high by 107 cm wide and was one of Velázquez's last paintings, produced in 1659, a year before his death. It shows Margaret Theresa of Spain who also appears in the artist's Las Meninas. Currently, the painting is in the Kunsthistorisches Museum.
This is one of the several court portraits made by Velázquez on different occasions of Infanta Margaret Theresa who, at fifteen, married her uncle, Leopold I, Holy Roman Emperor. She is the little infanta who appears in Las Meninas (1656). These paintings show her in different stages of her childhood; they were sent to Vienna to inform Leopold of what his young fiancée looked like.