The title of the painting, which is known in English as Mona Lisa, is based on the presumption that it depicts Lisa del Giocondo, although her likeness is uncertain. Renaissance art historian Giorgio Vasari wrote that "Leonardo undertook to paint, for Francesco del Giocondo, the portrait of Mona Lisa, his wife.

Lisa del Giocondo was a member of the Gherardini family of Florence and Tuscany, and the wife of wealthy Florentine silk merchant Francesco del Giocondo.[22] The painting is thought to have been commissioned for their new home, and to celebrate the birth of their second son, Andrea.[23] The Italian name for the painting, La Gioconda, means 'jocund' ('happy' or 'jovial') or, literally, 'the jocund one', a pun on the feminine form of Lisa's married name, Giocondo.[22][24] In French, the title La Joconde has the same meaning. 

The catalogue raisonné Leonardo da Vinci (2019) confirms that the painting probably depicts Lisa del Giocondo, with Isabella d'Este being the only plausible alternative.[27] Scholars have developed several alternative views, arguing that Lisa del Giocondo was the subject of a different portrait, and identifying at least four other paintings referred to by Vasari as the Mona Lisa.[28] Several other people have been proposed as the subject of the painting,[29] including Isabella of Aragon,[30] Cecilia Gallerani,[31] Costanza d'Avalos, Duchess of Francavilla,[29] Pacifica Brandano/Brandino, Isabella Gualanda, Caterina Sforza, Bianca Giovanna Sforza, Salaì, and even Leonardo himself.