She has long been rumoured to be the subject of Leonardo da Vinci's famed portrait, but German experts say they've discovered information that confirms the identity of the artist's real-life Mona Lisa.

Lisa Gherardini — wife of wealthy Florentine merchant Francesco del Giocondo — is the woman who inspired Leonardo's iconic 16th-century portrait, also known as La Gioconda, according to experts from Germany's Heidelberg University Library.

All doubts about her identity "have been eliminated by a discovery by [manuscript expert] Dr. Armin Schlechter," the library said in a statement on Monday.

In the past few years, experts at the library discovered notes made by a Florentine city official and friend of the artist within a collection of letters by Roman philosopher Cicero.

The comments, made by Agostino Vespucci in October 1503, make reference to Leonardo's work on three paintings — one of which was a portrait of the merchant's wife — at the time historians believe the artist completed Mona Lisa.

These notes are the earliest information linking Gherardini to Leonardo's portrait, the library said.

She was first linked to the painting in 1550, after comments made by painter, architect and Italian artist biographer Giorgio Vasari. However, some have dismissed his point of view because it came 50 years after the portrait was completed and some deemed him a questionable source.

Over the years, there has been much speculation about just whose mysterious smile inspired Leonardo's great work, with various theories ranging from the artist compiling many models' faces into one to his using of his own visage for the portrait, displayed at the Louvre Museum in Paris.