噬菌体(bacteriophage)，亦称噬体（phage）。
一类传染细菌的复合病毒。发现於20世纪初，发现後不久即开始用来治疗人类的腺鼠疫、霍乱等细菌疾病，但并不成功。1940年代随着抗生素的出现被放弃。1990年代随着抗药细菌的兴起，噬菌体的治疗潜力再度获得重视。噬菌体有成千上万种，每一种可能只能侵染一类或几类细菌。噬菌体的核心基因物质可能是核糖核酸（RNA）或去氧核糖核酸（DNA）。在噬菌体侵染宿主细胞时，这种裂解型噬体或毒性噬体会藉由裂解（迸裂）宿主细胞而释放出复制的滤过性病毒粒子。其他种类（称潜溶性噬体或温和性噬体）会将核酸植入宿主的染色体内，以在细胞分裂中复制。在此期间，噬菌体是无毒性的。这种滤过性染色体组以後会变得活跃，开始产生滤过性病毒粒子，破坏宿主细胞。赫尔希和蔡斯（M. Chase）在1952年把噬菌体用於一项着名的实验中，这个实验支持了DNA是基因物质的理论。由於噬菌体染色体组很小，而且很多都能在实验室制备，因此它们是分子生物学家最喜欢用的研究工具。对噬体的研究可帮助阐明基因的重组、核酸复制以及蛋白质合成。
English version：
bacteriophage
Any of a group of usually complex viruses that infect bacteria. Discovered in the early 20th century, bacteriophages were used to treat human bacterial diseases such as bubonic plague and cholera, but were not successful; they were abandoned with the advent of antibiotics in the 1940s. The rise of drug-resistant bacteria in the 1990s focused renewed attention on the therapeutic potential of bacteriophages. Thousands of varieties exist, each of which may infect only one or a few types of bacteria. The core of a bacteriophage's genetic material may be either DNA or RNA. On infecting a host cell, bacteriophages known as lytic or virulent phages release replicated viral particles by lysing (bursting) the host cell. Other types, known as lysogenic or temperate, integrate their nucleic acid into the host's chromosome to be replicated during cell division. During this time they are not virulent. The viral genome may later become active, initiating production of viral particles and destruction of the host cell. A. D. Hershey and Martha Chase used a bacteriophage in a famous 1952 experiment that supported the theory that DNA is the genetic material. Because bacteriophage genomes are small and because large quantities can be prepared in the laboratory, they are a favorite research tool of molecular biologists. Studies of phages have helped illuminate genetic recombination, nucleic-acid replication, and protein synthesis.