Description from Flora of China
Rhododendron megaphyllum I. B. Balfour & Forrest; R. regale I. B. Balfour & Kingdon Ward.
Shrubs or small trees, 3–10 m tall; branchlets stout, usually 8–15 mm in diam., grayish or whitish tomentose, glabrescent. Petiole flattened, winged, 15–35 mm, glabrescent; leaf blade leathery, broadly obovate to oblanceolate, broadest above middle, 10–32 × 5–17 cm; base cuneate; apex rounded, apiculate; abaxial surface with 2-layered indumentum, upper thick, grayish or rufous, hairs broadly cup-shaped, hardly fimbriate, lower layer compacted and thin; adaxial surface green, glabrous, midrib prominent abaxially, plane or impressed adaxially; lateral veins 12–15-paired, prominent abaxially. Inflorescence 15–25-flowered, rachis stout, 35–55 mm, sparsely tomentose. Pedicel 2.5–5 cm, brownish tomentose; calyx teeth 7 or 8, small, tomentose; corolla obliquely campanulate, pale yellow, with crimson basal blotch, 3.5–4.5 cm, lobes 8, suborbicular, ca. 1 × 1.2 cm, emarginate. Stamens 16, 1.5–2.5 cm; filaments glabrous; ovary ovoid, 8–10 mm, brown tomentose; style 2.5–3.5 cm, glabrous, stigma a swollen disk. Capsule cylindric, 25–40 × 8–10 mm, densely rufous-tomentose. Fl. May–Jun, fr. Oct–Nov.
Mixed or Abies forests; 2400–3700 m. W Yunnan [NE Myanmar].