Leonardo painted the Mona Lisa in Florence, most likely beginning around 1503 while also working on a mural for the city's council chamber^[3]. Vasari names the sitter as Lisa Gherardini, wife of the silk merchant Francesco del Giocondo, fourteen years her senior; her dowry included a family estate at San Silvestro in Chianti^[1]. Unlike many of Leonardo's other portraits, this was a simple commercial commission from a Florentine merchant rather than a courtly one, which makes his decision to keep working on it for years, and to never deliver it, unusual^[1]. Later French sources muddy the picture: a visitor to Leonardo's workshop in 1517 recorded that the artist described the painting as done for Giuliano de' Medici, a claim some historians think Leonardo emphasised once at the French court, to flatter a more useful patron than the Florentine merchant who had actually commissioned it^[1].

Leonardo called his technique sfumato, from the Italian for smoke, and used it to blur the outlines that usually carry a face's expression, particularly the corners of the mouth and eyes^[7]. Rather than drawing forms and filling them in, he built the face from successive thin, semi-transparent glazes over dark underpainting, so that colour and tone shift gradually with no hard edges^[2]. Even the pupils of her eyes are made from layered washes of pigment rather than a single stroke^[2]. Because the corners of the mouth and eyes are the features Leonardo deliberately left indistinct, her expression never quite settles, which is a large part of why viewers read so many different moods into the same fixed paint^[7].

The mountainous, geologically strange terrain behind Mona Lisa has attracted more scholarly attention than almost any other part of the painting. Leonardo had studied Tuscan geology in connection with canal-building plans along the Arno, and art historian Martin Kemp has argued the landscape depicts specific geological processes rather than an invented backdrop^[3]. Writers have also traced visual echoes between the folds of the sitter's clothing and hair and the flowing forms of the rivers and rock behind her, treating figure and landscape as a single unified system rather than a woman set in front of scenery^[3]. A winding path on the left of the composition has been read as an allusion to the story of Hercules choosing between virtue and vice, a detail that argues against the old theory that the sitter was a mistress rather than a wife^[7].