河豚毒素（英文：Tetrodotoxin，缩写：TTX）是一种强力的神经毒素，目前并没有有效的解毒剂，它会和神经细胞的细胞膜上的快速钠离子信道结合，令神经中的动作电位受阻截。

它的名字来自鲀形目，因为此目下的鱼类大多带有这种毒素，包括河鲀、二齿鲀、翻车鲀及鳞鲀等。虽然这种毒素常见于这些鱼类和其他生物体内，事实上它是由鱼类体内一种名为河豚毒素假交替单胞菌（Pseudoalteromonas tetraodonis；假交替单胞菌又名交替假单胞杆菌）的细菌所产生，其作用原理在1960年代早期由杜克大学的楢桥敏夫博士发现。

Tetrodotoxin, frequently abbreviated as TTX, is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several species that carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other aquatic animals (e.g., in blue-ringed octopuses, rough-skinned newts, and moon snails), it is actually produced by certain infecting or symbiotic bacteria like Pseudoalteromonas, Pseudomonas, and Vibrio as well as other species found in the animals.