Hydrothassa marginella is a Europe species of leaf beetles in the family Chrysomelinae Hydrothassa marginella grows to 3.4 - 4.5mm in length and are dark metallic blue and orange-yellow in colour.

[1] The pronotum is coloured yellowish with lateral margins.

[1] Hydrothassa marginella is a common and widespread species, active between the months of mid-April and August.

[2] Adults overwinter in grass tussocks.

[1] Hydrothassa marginella is prevalent in central and northern Europe.