It is important to remember cancers are not infectious and cannot be caught from someone. However, there are a number of different viruses that are thought to be contributing factors in the development of cancer.
For example, exposure to HPV (human papilloma virus) is known to increase the risk of developing some types of cancer. For further information about this, see the section about HPV.
Other viruses include the Epstein-Barr virus, which is linked to some types of lymphoma.
There is also a bacterial infection known as H-pylori which is linked to a rare type of stomach cancer.
See Q&As on this topic for a number of questions and answers about viruses and cancer.