Triadenum fraseri, known by the common names of bog St. John's wort, Fraser's St. John's wort, or Fraser's marsh St. John's wort, is a perennial flowering plant in the family Clusiaceae that appears natively in New England, northeastern and north Central United States and lower Canada in wetlands habitats of "bogs, marshes, swales, sedgy meadows, moist sandy (even marly) shores, conifer swamps and alder thickets". The species common name is named after John Fraser (1750–1811), a Scottish botanist and widely travelled plant collector.