The Roman Catholic Diocese of Rio Branco (Latin: Dioecesis Fluminis Albi Superioris) is a Latin suffragan see in the ecclesiastical province of the Metropolitan Archbishop of Porto Velho (Rondônia), in the upper Amazon River basin).

Its cathedral episcopal see is the Marian Catedral Nossa Senhora de Nazaré, dedicated to Our Lady of Nazareth, in the city of Rio Branco, Acre state, Brazil.

Pope Pius XI changed the name of the prelature to the Territorial Prelature of São Peregrino Laziosi no Alto Acre e Alto Purus on 10 December 1926, but its original name was restored on 26 April 1958 by Pope Pius XII.

The territorial prelature was elevated to a bishopric and hence renamed after its see as Diocese of Rio Branco by Saint John Paul II on 15 February 1986.

[1][2] As per 2014, it pastorally serves 443,000 Catholics (75.1% of 589,625 total) on 104,473 km2 in 32 parishes and 5 missions with 33 priests (23 diocesan, 10 religious), 22 deacons, 105 lay religious (19 brothers, 86 sisters) and 18 seminarians.