真核起始因子（英文：eukaryotic initiation factor，简称为eIF），又称为真核翻译起始因子，是指参与真核翻译起始这一过程的蛋白质。与原核起始因子只有三种（IF1、IF2、IF3）相比，真核起始因子种类多且复杂，目前已鉴定的真核起始因子共有12种。 通过这些真核起始因子之间以及不同的真核起始因子与核糖体、mRNA和起始tRNA之间的相互作用，来完成真核生物的翻译起始。因此相比于原核生物，真核生物的翻译起始过程更多得依赖于蛋白质与蛋白质以及蛋白质与RNA之间的相互作用，而非RNA与RNA间的相互作用。

Eukaryotic initiation factors (eIFs) are proteins involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of the functional ribosome around the start codon and also provide regulatory mechanisms in translation initiation. Several initiation factors form a complex with the small 40S ribosomal subunit and Met-tRNA_i called the 43S preinitation complex (PIC). Additional factors of the eIF4F complex (eIF4A, E, and G) recruit the 43S PIC to the five-prime cap structure of messenger RNA to promote ribosomal scanning along the mRNA to reach an AUG start codon. Recognition of the start codon by the Met-tRNA_i promotes GTP hydrolysis (or gated phosphate release) by specific initiation factors and initiation factor release, resulting in the 60S ribosomal subunit recruitment to form the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors, reflecting the greater biological complexity of eukaryotic cells. Eukaryotic translation requires at least twelve eukaryotic initiation factors, described below.