Protesters have been calling for Park to resign since revelations last week that her confidante and spiritual adviser Choi Soon-sil may have seen secret government documents and influenced policy.
In an apparent attempt to stem the scandal Wednesday, Park named three new senior officials to her cabinet.
Kim Byong-joon, a professor at Seoul's Kookmin University, will replace Hwang Kyo-ahn as prime minister, the president's office confirmed to CNN.
In South Korea, the premiership is largely a ceremonial position, but its holder serves as deputy to the president.
Yim Jong-yong and Park Seung-joo were named finance minister and national safety minister respectively. Both have previously served as cabinet ministers.
Multiple aides to President Park have resigned in the wake of the scandal, including four senior secretaries responsible for matters such as political affairs and policy coordination.
Analysts have doubted whether Park can survive the scandal simply by replacing her cabinet, given that it largely concerns her personal judgment.
In a televised apology, Park admitted Choi had looked at "some documents," and said "my heart is breaking" over the concerns caused to the public.