Nucleocytoplasmic large DNA viruses (NCLDVs) are a diverse group of viruses characterized by their large DNA genomes and complex structures. They primarily infect eukaryotic cells, including those of animals, plants, and fungi. NCLDVs are notable for their ability to replicate in the nucleus and cytoplasm of host cells, which distinguishes them from many other viruses. These viruses include well-known families such as Poxviridae, Asfarviridae, and Phycodnaviridae. NCLDVs can have significant ecological and medical implications, as they play roles in marine ecosystems and can cause diseases in various organisms, including humans. Their large genomes also provide insights into viral evolution and host interactions.