HELENA, DIOCESI di. - City and diocese in the State of Montana, in the United States of America. It comprises the western part of the State of Montana, namely the following counties: Lewis e Clark, Glacier, Pondera, Flathead, Lake, Lincoln, Missoula, Mineral, Sanders, Lodge, Silver Bow, Jefferson, Broadwater, Powell, Granite, Deer, Gallatin, Madison, Beaverhead, Meaghes, Wheatland, and part of Golden Valley, Teton, and Toole.
The diocese was founded by Pope Leone XIII on 7 March 1884. The territory first belonged to the jurisdiction of the vicariate of Nebraska, established in 1851, and subsequently to the apostolic vicariate of Montana.
The first bishop of H. was Msgr. J. B. Brondel (d. 1903). The diocese has an area of 140,360 sq. km., with a population of 240,000 inhabitants, of whom 60,000 were Catholics (1949). It has 53 parishes, 37 chapels, 49 missions, and 160 stations served by 93 diocesan priests and 12 religious. It has three male religious communities (Premonstratensians, Jesuits, and Irish Christian Brothers) and 10 female religious communities. It has a seminary, a College (Carroll), 5 diocesan and parish «high schools», and 19 parish elementary schools. In 1946 there were 187 conversions. The diocese is suffragan to Portland in Oregon; the Cathedral is dedicated to St. Helena.