The dog, named Harajuku B****, lived for 23 years and was deeply loved by the actor and media personality.
“Today, my heart breaks as I say goodbye to my precious chihuahua, Harajuku B****,” Hilton, 42, wrote on Instagram to share the news on Monday (22 May).
“For an incredible 23 years, she filled my life with so much love, loyalty, and unforgettable moments.”
Hilton added that she is currently experiencing “immense pain” over the death of Harajuku B****, calling the dog a “loyal friend” who was always by her side at “every twist and turn” of life.
She wrote: “She lived a long, beautiful and iconic life, surrounded by love until her final peaceful slumber. Words cannot express the immense pain I’m feeling right now.”
The “Stars Are Blind” singer wrote that the chihuahua was a “tiny ball of love” who “brightened up even the darkest of days”.
“We shared so many memories, laughter and tears.”
Hilton has been met with supportive comments from fans, many of whom also commented their shock after learning the dog’s age.
The Maleficent actor Elle Fanning commented: “An unbearable pain…. Rest peacefully sweet baby!”
A fan added: “She was 23? That’s amazing!”
Chihuahuas have a life expectancy between 12 and 20 years.
Another commented: “23 years! You are so blessed to have each other for so long.”
Hilton has had 10 dogs over the years, including Peter Pan, Marilyn Monroe, Slivington, Princess Paris Jr. and Prince Hilton, The Pom, Prince Baby Bear, with chihuahua being one of her favourite breeds of dog.
The first dog Hilton owned was the iconic chihuahua named Tinkerbell Hilton, who died in 2015 aged 14.
Last year, Hilton pleaded with fans to help her find one of her chihuahuas, named Diamond Baby who was missing since September.
The star expressed that she was at a “loss for words” after the dog disappeared through an open door in her home.
She wrote at the time: “We have hired a pet detective, a dog whisperer, a pet psychic and looking into dog finding drones now. I’m doing everything in my power to get her back.”
At the time of writing, Diamond Baby is still missing.