He showers her with attention and pays for two personal maids to provide 24-hour care for her at his mansion in Paris.
He admits he dotes on her so much that she is like a "kept woman".
Now Karl Lagerfeld has claimed that he would marry his pet cat if he could.
The 77-year-old fashion guru said that he never thought it was possible to love 22-month-old Choupette as much as he does.
German-born Lagerfeld's devotion to the white siamese is the stuff of legend even within the excesses of the couture industry.
Choupette (the name is said to be French for Herbie) dines at her owner's table on her own special pillow, has been pictured with her personal iPad and has a Twitter account with nearly 28,000 followers. It describes her as "a famous beauty who refuses to eat on the floor & my maids pamper my every need".
There is also a Facebook site in her name, with over 2000 'likes', or friends.
It pictures her about to tuck into a king prawn cake to celebrate her first birthday last August. Lagerfeld is so enamoured of the animal that her eyes are said to have been the inspiration for a cornflower-blue couture collection for Chanel, the fashion house for which he is head designer.
When Lagerfeld is not at home the maids, apparently named Francoise and Marjorie, write down everything she does in little books so he can catch up on it later. Choupette is said to prefer Francoise of the two women.
In a TV interview Lagerfeld said that, much to his disappointment, there is "no marriage, yet, for human beings and animals".
"I never thought that I would fall in love like this with a cat."
Lagerfeld adopted Choupette a year ago after looking after her for a friend for two weeks. He refused to give her back, and the pair have been inseparable ever since. The cat has even starred in her own film for the luxury fashion website Net-a-Porter.
Lagerfeld has described Choupette's coat as 'snow white with touches of caramel around the eyes, ears and on her endless boa-like feather tail'. In an interview with Harper's Bazaar he revealed that when Choupette fell sick he summoned a doctor in the middle of the night because he could not bear to wait until morning.
Choupette is brushed twice a day, every day, and is given regular manicures. Her favourite activities supposedly include running around, chasing big fleas in her private garden and tearing up pieces of paper.
The most special moments for Lagerfeld, he says, are when she gets on his papers while he is working, or when she brings all her toys to his bed as a present for him.
Lagerfeld is renowned for his eccentricities, and in one period is said to have lost 40kg by drinking nothing but Diet Coke and eating stewed vegetables.
- DAILY MAIL