中间纤维（英语：Intermediate filaments，IF，又译中间丝）直径10纳米(nm)左右，介于7 nm的肌动蛋白微丝和25 nm的微管之间。与后两者不同的是中间纤维是最稳定的细胞骨架成分，它主要起支撑作用。中间纤维在细胞中围绕着细胞核分布，成束成网，并扩展到细胞质膜，与质膜相连结。中间纤维没有正负极性。它们是一个相关的蛋白质家族, 分享共同的结构和串行特征。大多数类型的中间纤维存在于细胞质，但有一种类型的中间纤维–核纤层蛋白存在于细胞核。

Intermediate filaments (IFs) are cytoskeletal components found in the cells of many animal species. They are composed of a family of related proteins sharing common structural and sequence features. Intermediate filaments have an average diameter of 10 nanometers, which is between that of 7 nm actin (microfilaments), and that of 25 nm microtubules, and they were initially designated 'intermediate' because their average diameter is between those of narrower microfilaments (actin) and wider myosin filaments found in muscle cells. Most types of intermediate filaments are cytoplasmic, but one type, the lamins, are nuclear.