The class Lycopodiopsida includes the clubmosses. These plants are often loosely grouped as the fern allies. The Lycopodiopsida traditionally included all the clubmosses, including Selaginella and Isoetes. However, subdivisions within the Division Lycopodiophyta are now considered ancient enough to warrant higher-level separation in accordance with cladistics.

The clubmosses are thought to be structurally similar to the earliest vascular plants, with small, scale-like leaves, homosporous spores borne in sporangia at the bases of the leaves, branching stems (usually dichotomous), and generally simple form.

The Class Lycopodiopsida as interpreted here contains a single living order, the Lycopodiales, and a single extinct order, the Drepanophycales.