Cleistoblechnum is a genus of ferns in the family Blechnaceae, subfamily Blechnoideae, with a single species Cleistoblechnum eburneum, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus is accepted in a 2016 classification of the family Blechnaceae, but other sources sink it into a very broadly defined Blechnum, equivalent to the whole of the PPG I subfamily.

The natural habitat of Cleistoblechnum eburneum is subtropical or tropical moist lowland forests. It is threatened by habitat loss. It is native to China and Taiwan.

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