Nepenthes tenax (from Latin: tenax = tenacious) is a lowland species of tropical pitcher plant native to northern Queensland, Australia. It is the third Nepenthes species recorded from the continent and its second endemic species. N. tenax is closely related to the two other Australian Nepenthes species: N. mirabilis and N. rowanae.
N. tenax grows to a height of around 100 cm with pitchers rarely exceeding 15 cm. The stem is usually self-supporting. In its natural habitat, it is sympatric with N. mirabilis and N. rowanae. Two natural hybrids involving these species have been found.