结构基因（英语：structural gene）是指基因编码的产物为调节因子（调控基因）以外的蛋白质的基因，可以用于编码结构蛋白、酶或不涉及调控的非编码RNA。

这些基因对细胞的形态和功能特征非常重要。在真核生物中，这些基因是以片段化的形式存在，即分为外显子和内含子。但在原核生物中，这些基因是连续的，甚至几个功能相关的基因与调控基因组成一个操纵子来共同转录。

如在乳糖操纵子中，结构基因编码的就是与乳糖代谢有关的酶，这三个基因是：

A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). It may code for a structural protein, an enzyme, or an RNA molecule not involved in regulation. Structural genes represent an enormous variety of protein structures and functions, including structural proteins, enzymes with catalytic activities and so on. These genes are needed for the morphological or functional traits of the cell. In eukaryotes, these occur in split-form, segmented into introns and exons. But in prokaryotes, these are continuous. The structural genes are concerned with the synthesis of a polypeptide chain or a number of polypeptide chains and are also concerned with the synthesis of different types of RNA required during protein synthesis. Structural genes are different from regulatory or promoter genes, as they serve the significant purpose of actually transcribing for proteins.