染色体着丝粒（centromere），又称中节，主要作用是使复制的染色体在有丝分裂和减数分裂中可均等地分配到子细胞中。在很多高等真核生物中，着丝粒看起来像是在染色体一个点上的浓缩区域，这个区域包含着丝点（希腊语kínesis 运动；chóros 部位），又称主缢痕（primary constriction）。

着丝粒（染色体的主缢痕）为染色质的结构，将染色体分成二臂，在细胞分裂前期和中期，把两个姐妹染色单体连在一起，到后期两个染色单体的着丝粒分开。着丝粒两侧各有一个由蛋白质构成的3层盘状特化结构，为非染色体性质物质的附加物，称为着丝点。

The centromere is the part of a chromosome that links sister chromatids or a dyad. During mitosis, spindle fibers attach to the centromere via the kinetochore. Centromeres were first defined as genetic loci that direct the behavior of chromosomes.

The physical role of the centromere is to act as the site of assembly of the kinetochore - a highly complex multiprotein structure that is responsible for the actual events of chromosome segregation - i.e. binding microtubules and signalling to the cell cycle machinery when all chromosomes have adopted correct attachments to the spindle, so that it is safe for cell division to proceed to completion and for cells to enter anaphase.