Tardisia is an extinct genus of vicissicaudatan arthropod known from the upper Carboniferous Mazon Creek fossil beds in northern Illinois.

[1] Tardisia lacks eyes, with a head shield (the frontal end is lost on the holotype, but according to descriptions and the paratype it was likely sub-semicircular) smaller than the first tergite.

The trunk comprises seven tergites in the thorax, four with overlapping margins, and a postabdomen composed of the eighth segment, which lacks wide pleurae and instead bears a pair of caudal appendages.

The trunk's width slightly increases with the widest section (roughly 6 6 mm (0.24 in) wide) being the third tergite, afterwards steadily decreasing towards the posterior.

[1] Pygmaclypeatus daziensis Retifacies abnormalis Squamacula clypeata Protosutura Trilobitomorpha Molaria spinifera Emeraldella brocki Emeraldella brutoni Sidneyia inexpectans Tardisia broedeae Cheloniellida Carimersa neptuni Kodymirus vagans Eozetetes gemelli Aglaspidida Tardisia is likely a vicissicaudatan, due to sharing features such as the number of trunk segments and the postabdomen ending in caudal appendages.