转染(英语：Transfection)是将外源遗传物质(DNA或RNA)植入细胞的一种过程，常用来描述非病毒入侵的基因转殖方式，相较于转化（英语：transformation，又译转型）用于植物、细菌及癌细胞的扩散，转染则常被用来形容外源基因植入动物细胞，而病毒入侵的基因转殖方式则称为转导(英语：Transduction)。

动物细胞的转染作用方式如下，在细胞膜上开出一个暂时性的小孔，使细胞较容易摄取外源基因(可经由磷酸钙携带进入细胞)，借由电穿孔法、细胞挤压法即可制造孔洞、或将细胞及外源基因浸泡在充满脂质体的液体中，脂质体将会包住外源基因，然后融入细胞膜，并将外源基因释放到细胞内部。

Transfection is the process of deliberately introducing nucleic acids into cells. The term is often used for non-viral methods in eukaryotic cells. It may also refer to other methods and cell types, although other terms are preferred: "transformation" is more often used to describe non-viral DNA transfer in bacteria and non-animal eukaryotic cells, including plant cells. In animal cells, transfection is the preferred term as transformation is also used to refer to progression to a cancerous state (carcinogenesis) in these cells. Transduction is often used to describe virus-mediated DNA transfer.