Virus and virus-like particle (VLP) structures are diverse. This allows them to be engineered for intratumoural immunotherapy. Mammalian viruses include the herpes simplex virus 1 (TVEC; Protein Data Bank ID (PDB): 6CGR), adenovirus (DNX-2401; PDB: 6CGV) and poliovirus (PVSRIPO; PDB: 1POV). TVEC is currently approved for melanoma, and DNX-2401 and PVSRIPO are currently being tested in clinical trials. Cowpea mosaic virus (CPMV; PDB: 1NY7), M13 bacteriophage (PDB: 2MJZ), the Alphaflexiridae plant viruses papaya mosaic virus (PapMV) and potato virus X (PVX; PDB: 4DOX), cowpea chlorotic mottle virus (CCMV; PDB: 1ZA7), Qβ bacteriophage (PDB: 1QBE) and MS2 bacteriophage (PDB: 2MS2) are currently in the preclinical development pipeline. Viruses and VLPs can deliver Toll-like receptors (TLRs) and stimulator of interferon gene (STING) agonists.