Balthus was born Balthasar Klossowski in Paris. 

He decided to become a nobleman and called himself Count Klossowski de Rola. His father later suggested dropping the fake nobleman schtick and using the name Balthus. Just like Madonna, Prince, Cher, and Sting, Balthus has no first or last name, it's just Balthus.

He married an aristocrat named Antoinette de Watteville. She was also an elite model, but looks are not everything, and they separated after eight years.

Balthus had two children from this marriage to Antoinette, Thaddeus and Stanislas (Stash) Klossowski. They recently published a book of letters by their father and mother.

After separating from Antoinette, Balthus moved into Chateau de Chassy to live with his rebellious niece Frédérique Tison, who was only 16.

Early on, his work was admired by writers and fellow painters. His circle of friends in Paris included writers Albert Camus, Pierre Jean Jouve, and Antoine de Saint-Exupéry, the photographer Man Ray, the playwright and actor Antonin Artaud, and the painters André Derain, Joan Miró, André Breton, Pablo Picasso, and Alberto Giacometti. Later in his life he would move to Rome, where he became friends with the filmmaker Federico Fellini, the Wes Anderson of Italy.

Balthus adopted a street cat and began to make a series of 40 drawings depicting his adventurous life with Mitsou, the cat; their encounter, their love affair, and Mitsou's departure forever, and the sadness of its loss.  

His mother's lover was poet Rainer Maria Rilke, who was taken by Balthus' artwork, became his patron early on, and published Balthus' drawings in a booklet in 1921 titled "Mitsou 40 images." Balthus' mother lived with her husband and with Mr Rilke, and some speculate that Rilke was actually Balthus' biological father, which would make Balthus a descendant of Lord Byron, which he would have really liked.

Balthus was one of the few artists to have his work represented in the Louvre while still alive. Pablo Picasso sold Balthus' painting The Children (1937) to the  museum from his private collection.

Bono, lead-singer of U2, sang at Balthus' funeral in 2001.