The 26-year-old turned herself in to authorities at Los Angeles County Jail on Sunday, her lawyer confirmed.
She appeared at the MTV Movie Awards hours earlier, where she told reporters: "I'm definitely scared, but I'm ready to face my sentence."
The socialite will serve only half of her sentence - about 23 days - after being given credit for good behaviour.
She will be separated from the main prison population in a block that contains 12 cells, each holding two people.
It is reserved for celebrities, public officials, police officers and other high-profile inmates.
The unit is part of the Century Regional Detention Centre in Lynwood, California, which holds more than 2,000 prisoners.
The heiress-turned-pop singer was arrested for driving under the influence last September and was issued probation, which she violated several times by driving with a suspended licence.
Hilton made her final public appearance at the MTV Movie Awards on Sunday, where host Sarah Silverman received cheers for mentioning her impending jail sentence.
'Positive' attitude
"Even though this is a really hard time, I have my family, my friends and my fans to support me, and that's really helpful," Hilton told reporters.
The heiress said she had been given the option of going to a "pay jail" but declined.
"I'm going to do the time and I am going to do it the right way.
"I'm using it in a positive way and when I come out, I can't wait to start my new life and be even stronger than I am now."