SEOUL—South Korean authorities arrested former President Park Geun-hye after a court ruled she should be held while prosecutors accusing her of bribery and abuse of power seek an indictment, confining her to a prison cell just three weeks after she was removed from office.

Ms. Park, 65 years old, will be jailed in the latest chapter of a wide-ranging corruption scandal that has already led to her impeachment and put the country’s most powerful businessman, the de facto head of the Samsung conglomerate, behind bars. Ms. Park...