Park became South Korea's first woman president in 2013, casting herself in the role of the daughter of the nation, incorruptible and beholden to none.

Less than four years later, she was impeached and ousted after a corruption scandal sparked huge street protests.

On Friday, Justice Minister Park Beom-kye told reporters the former leader was included in a list of people receiving "special amnesty", and was pardoned from "a perspective of national unity".

The 69-year-old was serving a 20-year prison sentence for bribery and abuse of power, with another two years after that for election law violations.

Park was hospitalised several times this year, and South Korea's Yonhap news agency reported that her poor health was a factor in the decision to grant the pardon.

The episode exposed shady links between big businesses and politics in South Korea, with Park and her close friend Choi Soon-sil accused of taking bribes from conglomerates, including Samsung Electronics, in exchange for preferential treatment.

The resulting public backlash against Park and her conservative party helped propel the left-leaning Moon Jae-in into power.

Moon's presidency ends in March. The constitution limits presidents to a single five-year term.

In January, when the end of Park's trial process made her legally eligible for a pardon, Moon's office had said it was "not appropriate" to discuss amnesty at the time.

It was a "historical lesson" that a former president had committed acts that meant she had to serve a prison sentence, the Blue House had said at the time.

"This should never happen again."

Park was also hit with hefty fines along with her prison sentence.

South Korean prosecutors said in March this year they had seized the ex-president's house after she failed to pay a $19 million penalty for corruption.

South Korean presidents have frequently ended up in prison after their time in power, usually once their political rivals have moved into the presidential Blue House.

Chun Doo-hwan and Roh Tae-woo, former army generals who served jail terms in the 1990s for corruption and treason after leaving office, received presidential pardons after serving about two years.

Ex-president Roh Moo-hyun killed himself in 2009 after being questioned over graft allegations involving his family.

Lee Myung-bak, the only living ex-president aside from Park, is currently serving a prison sentence over corruption.