Phallus tenuissimus is a species of fungus in the stinkhorn family.

Found in Jingdong Yi Autonomous County in Yunnan, China, it was described as new to science in 2005.

Its fruit bodies feature a conical to bell-shaped cap up to 20 mm (0.8 in) high by 4–7 mm (0.16–0.28 in) wide, covered by dark greenish-brown gleba (spore mass).

The cap is supported by a slender, cylindrical stipe measuring 50–70 mm (2.0–2.8 in) long and 2–4 mm thick.

The authors place it in the section Reticulati of genus Phallus on account of its reticulate cap.