Dicksonia sellowiana, the xaxim, or samambaiaçu or imperial samambaiaçu, is an arborescent fern in the family Dicksoniaceae, native to the tropical Americas.

In the South American Atlantic Forest biome, it is found in: Southeastern Brazil in the states of Minas Gerais, Rio de Janeiro, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul; in northeast of Argentina within Misiones Province; and in eastern Paraguay.

Dicksonia sellowiana has an erect and cylindrical caudex, reaching sometimes more than 10 metres (33 ft) high, the fronds are bipinnate and 2 m (6 ft 7 in) long.

Due to illegal extraction, the species is at risk of extinction.

Variations are sometimes treated as separate varieties, which include:[1]