The answer is Guernica.

I had to look it up for a project.

I don't know if i'd call it the "single most important work of the 20th century" but the most famous mural Picasso painted was "Guernica". See the Related Links section below for a picture of it.

Answer 2: Only Guernica is not a mural It is painted on a large canvas.

Pablo Picasso clearly adored women, it certainly seems, given the amount of paintings, drawings and other art of Picasso that he made he, to some degree objectified the women he loved. Of the many women that Picasso loved, he only married two of them. It's uncertain if there is a definitive number of mistresses Picasso had. It is uncertain what the questioner means by mistress, but that Picasso had mistresses, kept mistresses and loved them is indeed certain. Of the many women Picasso loved, there are at least eight of those women who were also adored and lovingly rendered by the artist. These eight women were:

Ferdinande Oliver

She was the subject of many of Picasso's Rose Period paintings and was his first real long term relationship with a women. Picasso met her in Paris in 1904. His Rose period was from 1905 to 1907. Their relationship lasted seven years. Ferdinande left Picasso in 1912 after Pablo had all ready taken in interest in Marcelle Humbert also known as...

Eva Gouel

Even though this relationship was cut short by her tragic death, the evidence of Picasso's love for this woman can be found in certain paintings where the artist painted "I love Eva" in some of his paintings. All though he clearly loved this woman and was devastated by her death, while she lay sick on her death bed, Picasso managed to find time for a woman by the name of Gaby Lespinasse.

Olga Khokhlova

Met Picasso while he was in Rome designing the ballet "Parade", that would be performed by the Ballet Russe. They married in 1980 and for the next decade fought and argued and found it difficult to get along. Their tastes were different, even their lifestyles clashed. In spite of this, they had one son Paul but in 1927 Pablo Picasso had met another woman and separated from Olga. They never divorced so Picasso didn't have to surrender half of his wealth, and it remained that way until Olga's death in 1955.

Marie-Therese Walter

In 1927 Picasso took up residence with this seventeen year old girl in a flat across the street from his home with his wife Olga. Even though directly across the street from his wife he somehow managed to hide in plain sight and kept this relationship from his wife until Marie-Therese's pregnancy in 1935. All though Marie-Therese is the inspiration for Vollard Suite by Picasso, he fell in love with another women in 1936 and Marie-Therese was left rejected. She would hang herself in 1977 four years after Picasso's death.

Dora Maar

Picasso met this artist and photographer when she documented his painting of Guernica. They were inseparable until Picasso left her for Francoise....

Francoise Gilot

A young art student Picasso met in 1943 they would have two children together and themselves stayed together near a decade. But Gilot, frustrated with his abusive nature and unfaithfulness finally left him.

Genevive Laporte

Picasso first met Genevive when she interviewed him for a school paper. She was seventeen at the time. There time was brief together and Laporte left Picasso around the same time Francoise Gilot left him. The art inspired by Genevive is sometimes referred to as Picasso's "gentle period".

Jacqueline Roque

Suffering through the pain of this double whammy rejection, in 1953 Picasso met Jacqueline and in 1961 at 79 years of age Picasso married Jacqueline making her his second wife. They remained together until Picasso's death in 1973 and of all the women that he loved he created more works of art inspired by Jacqueline than any other women he had known. In 1986 Jacqueline shot herself.

There were, of course, many other women who Picasso had dallied with, but it was these eight who seemed to matter the most.
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