Monday marks the fourth anniversary of the sinking of the Sewol-ho ferry.
On April 16th, 2014, the vessel, carrying 476 passengers and crew, sank off Korea's southwestern coast.
More than three-hundred people, mostly high school students, lost their lives.
Despite a months-long search in which the ferry was raised from the sea last year, the remains of five people have still not been found.
South Korean President Moon Jae-in, in a post on Facebook Sunday, asked the nation to remember the disaster and share their sorrow.
He promised to make the nation safer and that the government will continue its investigation into the search for the bodies of the missing.
A government-led memorial ceremony will take place in Ansan, Gyeonggi-do Province on Monday, where most of the victims are from.
Others will be held at Mokpo New Port and Paengmok-hang harbor in southern Jeollanam-do Province -- sites near where the ferry sank and was recovered.