Sonchus sinuatus, synonym Dendroseris macrantha, is a species of flowering plant in the family Asteraceae.

It is endemic to the Juan Fernández Islands of Chile.

[1] The species was first described in 1833 as Rea macrantha.

[2] In 2012, based on molecular phylogenetic evidence, it was shown that Dendroseris was embedded within the genus Sonchus, and all its species were transferred to that genus and placed in Sonchus subg.

[4] As the combination Sonchus macranthus had already been used for a different species, the replacement name Sonchus sinuatus was published.