Herbs, erect, not scapose, 1.2-2 × 1-2 dm, glabrous, green. Stems spreading, without persistent leaf bases, up to 8 height of plant; caudex stems matted; aerial flowering stems erect, slender, solid, not fistulose, 0.8-1 dm, glabrous, densely tomentose among leaves. Leaves basal, 1 per node; petiole 3-5 cm, finely strigose; blade cordate to truncate or rarely reniform, (1-)1.5-2.5 × 1.5-2.5(-3) cm, glabrous except for fine hairs on margins and veins, margins plane. Inflorescences cymose, (4-)10-20 × 5-15(-20) cm; branches dichotomous, glabrous; bracts 3, scalelike, triangular, (2-)3-5 mm. Peduncles slender, erect, (0.5-)1-3 cm. Involucres 1 per node, campanulate, 1-1.5 × 2-2.5 mm, glabrous; teeth 5, erect to spreading, 1-1.3 mm. Flowers 1-2 mm; perianth yellow, glabrous except for fine white hairs along midrib; tepals connate proximal 3, slightly dimorphic, those of outer whorl lanceolate, 1.3-1.7 mm wide, those of inner whorl narrowly lanceolate, 0.7-0.9 mm wide; stamens exserted, 1.8-2.2 mm; filaments glabrous or nearly so. Achenes light brown, 1.5-2 mm, glabrous. 2n = 40. Flowering May-Sep. Eroded gypsum clay hills and fans, creosote bush communities; of conservation concern; 900-1100 m; N.Mex. Eriogonum gypsophilum is a federally listed threatened species. It is known only from three locations (Seven River Hills, south of Black River Village, and in the Ben Slaughter Draw/Hay Hollow drainage) in Eddy County. Its relationship to the rest of the species in subg. Eucycla is obscure. It may be more closely related to E. orcuttianum S. Watson, a large shrub of Baja California, Mexico, than to anything in the Rocky Mountain flora.