This is "A Female Saint" painted in the Italian north, possibly Ferrara or Bologna. The woman depicted looks directly at us and presses her right hand against her breast. Her oval face, strong regular features and plaited bound hairstyle give her the appearance of a woman from ancient Rome.
The painting's style is reminiscent of Raphael’s "Donna Velata" in Florence, and it's likely that our painter was influenced by his work. The frame dates back to the 17th century and may be original to the painting. It's suffered from the same type of worm damage as the picture itself, which suggests they were created around the same time.
The subject's identity is not clear-cut, but some art historians believe she might represent Saint Agatha, a saint known for being martyred in AD 251 by having her breasts cut off. The painting's style and technique are also comparable to that of Dosso Dossi and Parmigianino, two artists active in the Italian north during the 16th century.
Despite some uncertainty about its origins, technical analysis suggests this painting dates back to the 16th or possibly 17th century. It's painted on wood with oil, which was a common medium for artists of that time.
A Female Saint hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.