运铁蛋白（英语、德语、瑞典语：Transferrin，源于拉丁语：transferre「结转」及ferrum「铁」）主要由肝脏制造，是一种糖蛋白。它一共有两个铁离子结合位，每个结合位可以与一个铁离子结合。在羧基端（carboxyl terminal）的结合位与铁离子有很高的亲和力，只会与铁离子结合。在胺基端的结合位则是可以与其他离子结合，亲和力高低如下：铁>铬>锰>镉>镍。三价铁离子与运铁蛋白的结合需要一个阴离子的存在，通常是碳酸氢盐。未与铁离子结合的运铁蛋白称为原运铁蛋白（apo-transferrin）。

Transferrins are iron-binding blood plasma glycoproteins that control the level of free iron in biological fluids. Human transferrin is encoded by the TF gene.

Transferrin glycoproteins bind iron tightly, but reversibly. Although iron bound to transferrin is less than 0.1% (4 mg) of total body iron, it forms the most vital iron pool with the highest rate of turnover (25 mg/24 h). Transferrin has a molecular weight of around 80 KDa and contains two specific high-affinity Fe(III) binding sites. The affinity of transferrin for Fe(III) is extremely high (association constant is 10 M at pH 7.4) but decreases progressively with decreasing pH below neutrality.