The Roman Catholic Diocese of Grajaú () is a diocese located in the city of Grajaú in the ecclesiastical province of São Luís do Maranhão in Brazil.
History 10 February 1922: Established as territorial prelature of São José do Grajaú from the Archdiocese of São Luís do Maranhão 4 August 1981: Promoted as Diocese of São José do Grajaú 9 October 1984: Renamed as Diocese of Grajaú
Leadership Ordinaries, in reverse chronological order Bishops of Grajaú (Roman rite), below Bishop Franco Cuter, OFMCap (1998.01.21 – 2016.12.07) Bishop Serafino Faustino Spreafico, OFMCap (1987.05.13 – 1995.11.02) Bishop Tarcísio Sebastião Batista Lopes, OFMCap (1984.10.08 – 1986.12.19), continuing when diocese was renamed; appointed Bishop of Ipameri, Goias Bishops of São José do Grajaú (Roman Rite), below Bishop Tarcísio Sebastião Batista Lopes, OFMCap (1984.04.04 – 1984.10.08); diocese renamed Bishop Valenti Giacomo Lazzeri, OFMCap (1981.08.04 – 1983.01.06) Prelates of São José do Grajaú (Roman Rite), below Bishop Valenti Giacomo Lazzeri, OFMCap (1971.05.18 – 1981.08.04) Bishop Adolfo Luís Bossi, OFMCap (1966.02.19 – 1970.08.22) Bishop Emiliano José Lonati, OFMCap (1930.01.10 – 1966.02.19) Bishop Roberto Julio Colombo, OFMCap (1924.12.18 – 1927.11.08) Fr. Roberto de Castellanza, OFMCap. (Apostolic Administrator 1922 – 1924)
Coadjutor bishop Adolfo Luís Bossi, OFMCap (1958-1966)
References GCatholic.org Catholic Hierarchy Diocese website (Portuguese)