One hundred and three Korean Martyrs are canonized by Pope John Paul II in Seoul.

The Korean Martyrs were the victims of religious persecution against Catholics during the 19th century in Korea. Among them are 103 Saints and 124 Blesseds officially recognized by the Catholic Church.

Canonization is the declaration of a deceased person as an officially recognized saint, specifically, the official act of a Christian communion declaring a person worthy of public veneration and entering their name in the canon catalogue of saints, or authorized list of that communion's recognized saints.

Pope John Paul II was head of the Catholic Church and sovereign of the Vatican City State from 16 October 1978 until his death in 2005. He was the first non-Italian pope since Adrian VI in the 16th century, as well as the third-longest-serving pope in history, after Pius IX and St. Peter.

Seoul, officially Seoul Special Metropolitan City, is the capital and largest city of South Korea. The broader Seoul Metropolitan Area, encompassing Seoul, Gyeonggi Province and Incheon, emerged as the world's sixth largest metropolitan economy in 2022, trailing behind New York, Tokyo, Los Angeles, Paris, and London, and hosts more than half of South Korea's population. Although Seoul's population peaked at over 10 million, it has gradually decreased since 2014, standing at about 9.6 million residents as of 2024. Seoul is the seat of the South Korean government.