The 25-year-old was also handed three years' probation and fined $2,048 (£1,010) at a court in California.
She was arrested in December after driving the wrong way down a Los Angeles motorway.
Ms Richie's sentence comes weeks after her Simple Life co-star Paris Hilton was released after 23 days in prison.
At the time of Ms Richie's arrest, police said she told them that she had taken a painkiller and smoked marijuana.
At a court appearance in February, she denied the charges.
The TV star, who is the daughter of singer Lionel Richie, entered the courthouse in Glendale with boyfriend Joel Madden, the lead singer of rock band Good Charlotte.
Superior Court Commissioner Steven K Lubell warned Ms Richie she would go to jail for a year if she violated the terms of her three years' probation, and called the facts of the case "pretty scary".
"Someone could have gotten killed or injured. The court does not want anything to happen to you," he told Ms Richie.
She has also been ordered to enrol in a drug and alcohol programme and must prove she has completed it by February.
"You are not to drive with any measurable amount of alcohol or drugs in your system," said Mr Lubell. "You are not to drive without a driver's licence," he added.
He told the court he would let the state Department of Motor Vehicles determine whether to suspend her driving licence or not.
Güncelleme Tarihi: 28 Temmuz 2007, 11:54