The painting’s fame was emphasized when it was stolen on 21 August 1911. The next day, Louis Béroud, a painter, walked into the Louvre and went to the Salon Carré where the Mona Lisa had been on display for five years. However, where the Mona Lisa should have stood, he found four iron pegs. Béroud contacted the section head of the guards, who thought the painting was being photographed for marketing purposes. A few hours later, Béroud checked back with the section head of the museum, and it was confirmed that the Mona Lisa was not with the photographers. The Louvre was closed for an entire week to aid in investigation of the theft.
French poet Guillaume Apollinaire, who had once called for the Louvre to be “burnt down”, came under suspicion; he was arrested and put in jail. Apollinaire tried to implicate his friend Pablo Picasso, who was also brought in for questioning, but both were later exonerated.
At the time, the painting was believed to be lost forever, and it was two years before the real thief was discovered. Louvre employee Vincenzo Peruggia had stolen it by entering the building during regular hours, hiding in a broom closet and walking out with it hidden under his coat after the museum had closed. Peruggia was an Italian patriot who believed Leonardo’s painting should be returned to Italy for display in an Italian museum. Peruggia may have also been motivated by a friend whose copies of the original would significantly rise in value after the painting’s theft. A later account suggested Eduardo de Valfierno had been the mastermind of the theft and had commissioned forger Yves Chaudron to create 6 copies of the painting to be sold in the United States while the location of the original was unclear. But the original remained in Europe and after having kept the Mona Lisa in his apartment for two years, Peruggia grew impatient and was finally caught when he attempted to sell it to the directors of the Uffizi Gallery in Florence; it was exhibited all over Italy and returned to the Louvre in 1913. Peruggia was hailed for his patriotism in Italy and served six months in jail for the crime.
In 1956, the lower part of the painting was severely damaged when a vandal threw acid at the painting. On 30 December of that same year, a young Bolivian named Ugo Ungaza Villegas damaged the painting by throwing a rock at it. This resulted in the loss of a speck of pigment near the left elbow, which was later painted over.
The use of bulletproof glass has shielded the Mona Lisa from more recent attacks. In April 1974 a “lame woman”, upset by the museum’s policy for disabled people, sprayed red paint at the painting while it was on display at the Tokyo National Museum. On 2 August 2009, a Russian woman, distraught over being denied French citizenship, threw a terra cotta mug or teacup, purchased at the museum, at the painting in the Louvre; the vessel shattered against the glass enclosure. In both cases, the painting was undamaged.