内部核糖体进入位点（英语：Internal ribosome entry site，简称为IRES）是指位于信使RNA（mRNA）串行中部为翻译起始而备用的一段核苷酸串行，为蛋白质生物合成这一更高级过程中的部分。通常来说，在真核细胞中，可仅在mRNA分子的5'端起始翻译，因为装配起始复合体是需要识别5'端帽的。

An internal ribosome entry site, abbreviated IRES, is a nucleotide sequence that allows for translation initiation in the middle of a messenger RNA (mRNA) sequence as part of the greater process of protein synthesis. Usually, in eukaryotes, translation can be initiated only at the 5' end of the mRNA molecule, since 5' cap recognition is required for the assembly of the initiation complex. The location for these sites is often in the 5'UTR, but can occur in many different places in an mRNA.