Nepenthes merrilliana (after Elmer Drew Merrill) is a tropical pitcher plant endemic to the Philippines. It produces some of the largest pitchers in the genus, rivalling those of N. rajah. The species is native to northern and central Mindanao as well as neighbouring Dinagat and Samar. Its presence in southern Mindanao is uncertain. It inhabits coastal forest areas on steep slopes at elevations of 0–1100 m above sea level. Nepenthes surigaoensis is closely related to N. merrilliana and was for a long time considered a heterotypic synonym of this species. Nepenthes samar is another closely allied species.

Natural hybrids