Wat Lum Mahachai Chumphon was established in the year 1691. Originally, there were two temples located nearby: Wat Lum and Wat Nern. Later, around 1920, His Holiness the Supreme Patriarch, Prince Vajirananavong, during his tenure as Phra Yanaworaphorn and while serving as the head of the Chanthaburi district clergy, visited the area to inspect the monastic community. He then decided to merge Wat Lum with Wat Nern into a single temple, naming it Wat Lum.