Clethra alnifolia, the coastal sweetpepperbush or summer sweet, is a species of flowering plant in the genus Clethra of the family Clethraceae, native to eastern North America from southern Nova Scotia and Maine south to northern Florida, and west to eastern Texas.

[3] The "pepper" part of the common name derives from the mature fruits, capsules which have a vague resemblance to peppercorns, however with no element of spiciness.

It grows in wet forests, pine flatwoods, wetlands, bogs and can be seen alongside woodland streams.

C. alnifolia is typically used as a shrub for natural gardens, or is placed alongside a stream or pond to delay erosion.

Both 'Ruby Spice',[5] with strongly pink flowers, and the dwarf 'Hummingbird'[6] have gained the Royal Horticultural Society's Award of Garden Merit (confirmed 2017).