软骨是人和脊椎动物特有的胚胎性骨骼，一种无血管组织。可分为透明软骨、弹性软骨和纤维软骨，为一种略带弹性的坚韧组织，在机体内起支持和保护作用。软骨是由软骨细胞、纤维和基质构成，其中基质占了体积的95%，而水分又占了基质的70%。基质的有机成分主要是多种蛋白，如软骨粘蛋白、胶原和软骨硬蛋白等。由于软骨没有血液供应，在基质中含有大量的第二型胶原和葡萄糖胺聚合糖（GAG）来帮助物质扩散。在胎儿和年幼期，软骨组织分布较广，后来逐渐被骨组织代替。成年人软骨存在于骨的关节面、肋软骨、气管、耳廓、椎间盘等处。

Cartilage is a flexible connective tissues, including the joints between bones, the rib cage, the ear, the nose, the bronchial tubes and the intervertebral discs. It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle.

Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body. Examples include the rings of the trachea, such as the cricoid cartilage and carina, the torus tubarius at the opening of the pharyngotympanic/auditory tube, the ala of the nostrils, and the auricle/pinna of the ear.