Hypericum undulatum, the wavy St Johns Wort, is a herbaceous perennial flowering plant native to western Europe and northern Africa.

Hypericum undulatum grows 1.5–12 cm (0.59–4.72 in) tall, typically erect or decumbent with a creeping or rooting base.

The herb typically has numerous to few narrow stems, each with four wings of tissue that bear black glands.

The leaves have three, occasionally four, pairs of main lateral veins that arise from the lower quarter of the midrib, as well as a dense tertiary reticulation.

This population, named H. boeticum by Pierre Edmond Boissier, has intermediate characteristics between H. undulatum and H. tetrapterum.

[1] Hypericum undulatum grows in non-calcareous fields and marshes, stream banks, fens, and acidic bogs at elevations from sea level to 2,700 m (8,900 ft).

Population sizes of the herb can vary greatly, increasing especially following reinstatement of grazing or burning in overgrown sites.

Decline of H. undulatum in localities is mostly due to habitat loss, typically resulting from agricultural intensification.

Managing populations of the herb in grasslands involves grazing in the summer and occasional burning in the winter.