The Roman Catholic Diocese of Cruzeiro do Sul () is a suffragan see in the ecclesiastical province of the Metropolitan Archdiocese of Porto Velho, Acre (state), westernmost Amazonian Brazil.
Its cathedral episcopal see is the Marian Catedral Nossa Senhora da Gloria, in the city of Cruzeiro do Sul, Acre.
As per 2014, it pastorally served 230,966 Catholics (80.6% of 286,462 total) on 126,633 kmò in 12 parishes and 99 missions with 25 priests (16 diocesan, 9 religious), 91 lay religious (16 brothers, 75 sisters) and 13 seminarians.