This paper reports the successful fabrication and characterization of a highly sensitive p-nitrophenol (p-NP) amperometric chemical sensor based on crystalline α-MnO₂ nanotubes. The α-MnO₂ nanotubes were successfully synthesized using a simple hydrothermal treatment of potassium permanganate (KMnO₄) and concentrated hydrochloric acid (HCl). The prepared nanotubes were examined in detail by using various analytical methods which revealed that the synthesized nanotubes are grown in very high density, possessing good crystallinity and high purity. The as-synthesized α-MnO₂ nanotubes were used for the fabrication of the p-NP chemical sensor which exhibited high sensitivity of 19.18 mA mM⁻¹ cm⁻² and a low detection limit of 0.1 mM. To the best of our knowledge, this is the first report that used α-MnO₂ nanotubes to fabricate a p-NP chemical sensor with such high sensitivity and low detection limit.