It has an area of 25,679 sq. km. with a population of 275,214 inhabitants, of whom 275,000 are Catholics. It comprises 13 parishes, served by 9 diocesan priests and 6 regular clergy, as well as 3 male and 4 female religious communities (Ann. Pont., 1952, p. 307).
The diocese was erected by Pope Pius XII with the apostolic constitution *Ad Dominici gregis* of 16 December 1944, by separating it from the Diocese of Piauí, which was simultaneously elevated to metropolitan status and renamed Teresina, of which Parnaíba became a suffragan see. The parish church dedicated to Our Lady of Victory became the cathedral of the new diocese. The first bishop was Msgr. Filippo Condurò Pacheco.
BIBL.: AAS, 37 (1943), pp. 133-35; J. B. Lehmann, *O Brasil Católico* 1947, Juiz de Fora 1947, pp. 268-70.