Park Geun-hye has been taken into custody over the corruption scandal that led to her dismissal.
After a court had approved, the 65-year-old was moved to a dentition center south of Seoul.
She is accused of allowing her close friend, Choi Soon-sil to extort money from large enterprises, in return for political favors.
Ms. Park, who was removed from her office earlier in the month, denies the claims.
She’s not the first South Korean President to be arrested over criminal allegations; two other former presidents were also arrested before her.
The warrant to detain Ms. Park was issued earlier by The Seoul Central District Court. She’s being investigated on charges of abuse of authority, leaking government secrets, bribery and coercion.
The warrant followed a nine-hour court hearing attended by Mr. Park on Thursday.
The statement from the court said:
“It is justifiable and necessary to arrest [Ms. Park] as key charges were justified and there is risk of evidence being destroyed.”
Live TV footage showed a black sedan carrying her to the detention center from the prosecutor’s office where she had been waiting.
Although it was the early hour, some 50 supporters gathered at the gate to greet her; they were waving national flags and demanded her release, the AFP news agency reported.
Before being formally charged, Ms. Park can be held for 20 days, and if convicted, she could face more than ten years in prison.
She lost her presidential immunity after a constitutional court upheld the decision of the parliament to impeach her.
The close friend, Ms. Choi is accused of using her presidential connections to pressure companies to give millions of dollars to non-profit organizations that she controlled.
Ms. Park is alleged to have been personally involved in this, by giving access to unacceptable level of official documents to Ms. Choi.
Judges had accused Ms. Park of breaking the law by allowing Ms. Choi to meddle in state affairs, and breaching guidelines on official secrets by leaking official documents.
Ms. Choi and Samsung’s acting head Lee Jae-yong have also been kept in the same detention center where Ms. Park had been sent. They are also involved in the same scandal and are being tried separately.
A loyal to Ms. Park, Hwang Kyo-ahn is the acting president and the election for a new president are going to be held on May 9.