Caenorhabditis macrosperma is a species of nematodes in the genus Caenorhabditis. Prior to 2014, it was referred to as C. sp. 18. The type isolate was collected in Nouragues, French Guiana.
This species groups with the C. nouraguensis/C. yunquensis branch in the 'Japonica' group, the sister clade to the 'Elegans' group, in the 'Elegans' supergroup.