Nepenthes rigidifolia /nɪˈpɛnθiːz ˌrɪdʒɪdɪˈfoʊliə/ is a critically endangered tropical pitcher plant endemic to Sumatra, where it grows at elevations of 1000–1600 m above sea level.

[4] The specific epithet rigidifolia is formed from the Latin words rigidus (rigid) and folia (leaves), and refers to the plant's stiff, coriaceous leaf blades.

[3] At the time, it was recorded as growing at an elevation of around 1600 m.[3] In 2004, Ch'ien Lee informally named the species N. alpicola and later N. aptera.

[5] Instead, the species was formally described[note a] later that year as N. rigidifolia by Pitra Akhriadi, Hernawati, and Rusjdi Tamin.

[6] Two years later, Hernawati and Akhriadi covered the species in their book, A Field Guide to the Nepenthes of Sumatra, and assessed its conservation status.

[2] Stewart McPherson observed N. rigidifolia at the type locality in 2007 and published an updated description of the species in his 2009 monograph, Pitcher Plants of the Old World.

A pair of fringed wings (≤2 mm wide) extends up to 2 cm below the peristome,[2] before narrowing to ribs.

A number of circular or slightly ovate nectar glands (≤ 0.1 mm wide) are concentrated on the underside of the lid, but no appendages are present.

[7] Flowers are produced on two-flowered partial peduncles bearing filiform basal bracteoles up to 2 mm long.

This unusual reproductive habit has also been observed in N. alba, N. ampullaria, N. attenboroughii, N. benstonei, N. philippinensis, N. sanguinea, and N. thai.

Some plants are completely glabrous, while others bear a covering of orange to brown hairs (≤1 mm long) on the stem, pitchers, tendrils, and portions of the inflorescence.

[1] This agrees with an informal assessment carried out in 2006 by Hernawati and Pitra Akhriadi, who also classified the species as critically endangered based on the IUCN criteria and using field data collected by the "Nepenthes Team" of Andalas University.

[7] If the type locality is the site of the last remaining population of this species then it is one of rarest Nepenthes known and "threatened with imminent extinction".

[4] In Pitcher Plants of the Old World, Stewart McPherson wrote that field studies are "urgently required" to properly assess its conservation status.

[3] Nepenthes rigidifolia differs from N. bongso, N. ovata and related species in having mostly ovoid upper pitchers (compared to infundibular in the others), distinctly thick and coriaceous laminae, and a narrower, cylindrical peristome with very short teeth.

[2] While recognising N. rigidifolia as a valid species in his Carnivorous Plant Database, taxonomist Jan Schlauer suggests that it may be conspecific with N. densiflora.

[5] Terrestrial pitchers of N. rigidifolia may superficially resemble those of N. spectabilis, but it can be distinguished from this species on the basis of its trap colouration, upper pitcher shape (largely ovate in N. rigidifolia versus predominantly cylindrical in N. spectabilis),[4] thinner leaves, and branched spur.

[4] This cross, which is only known from a single open rocky outcrop,[3] may now outnumber N. rigidifolia at the type locality (as observed by Stewart McPherson in 2007).

[4] The hybrid differs from N. rigidifolia in having narrower pitchers with a strongly infundibular base and distinct hip around the middle.

[3] Charles Clarke wrote of this cross: "Unlike N. ovata × N. spectabilis (from Gunung Pangulubao), this hybrid seems to combine the more attractive characteristics of both parent species, producing large, beautifully coloured pitchers".

Karo, around Sidikalang areas, 1000–1500 m, Dec 11, 2003, Nepenthes Team (Hernawati, P. Akhriadi & I. Petra), NP 354 (‘ANDA’–Holo, BO–Iso).