Spectators, athletes and officials were welcomed to the chiming of bells as a ceremony titled "Peace in Motion" got under way in the 35,000-seated Pyeongchang Olympic stadium.
North Korean leader Kim Jong-un's younger sister, Kim Yo Jong, who landed at the Incheon airport of Friday, was seen shaking hands with South Korean President Moon Jae-in during the opening ceremony.
In a rare show of unity, athletes from South and North Korea will march together under a "unification flag".
Earlier, a high-level North Korean delegation, led by Kim's sister arrived for a three-day visit.
|Loud cheers greeted the South and North Korean teams, as they marched together at the opening ceremonies on Friday [AP]|
For the next 17 days, an estimated 2,952 athletes from 92 countries will be competing for Olympic medals in 102 events across 15 different sports.
Some sporting events, like curling and ski jumping, started on Thursday.
Al Jazeera's Natasha Ghoneim, reporting from the South Korean city of Gangneung said: "This is South Korea's moment in the international spotlight."
This is the first time South Korea is hosting the Winter Olympics and it is the country's second Olympic event after the 1988 Summer Games in Seoul.
Residents told Al Jazeera that they are proud and excited to be hosting the Olympics again.
Many feel the Pyeongchang Games are a "good opportunity to promote South Korea".
"I hope that with North Korean athletes' participation this could be a Peace Olympics. And I hope we can achieve reunification between the South and the North," one spectator in Gangneung told Al Jazeera.
Another said: "Regardless of North Korea's participation, the Olympics should be a festival."
There has been an apparent thaw in relations between North and South Korea in recent weeks.
The two neighbours resumed cross-border talks last month.
In what was described as a major diplomatic breakthrough, North Korea said it would send a delegation of athletes and performers to the Pyeongchang Winter Olympics in South Korea.
North Korea staged a relatively toned down military parade to mark the 70th anniversary of its armed forces in its capital on Thursday.
Russians lose appeal
A last-minute appeal by 41 Russian athletes and coaches to take part in the games was rejected by the Court of Arbitration for Sport on Friday.
The Russians appealed against their exclusion by the International Olympic Committee, over the 2014 doping scandal at the Sochi Games.
Meanwhile, almost 170 Russian athletes have been cleared to compete, but since their country is banned, they will be flying a neutral Olympic flag.
The games, which cost an estimated $12.5bn, will run from February 9 to 25.