Megavirus is a type of giant virus that was first discovered in 2003. It is notable for its large size, with a genome that can contain over a million base pairs, making it one of the largest known viruses. Megaviruses primarily infect amoebas and are found in various environments, including freshwater and marine ecosystems. These viruses are part of a group known as nucleocytoplasmic large DNA viruses (NCLDVs), which have complex structures and large genomes. The discovery of Megavirus has expanded our understanding of viral diversity and evolution, highlighting the complexity of life forms that exist beyond traditional definitions of viruses.