HIV superinfection (also called HIV reinfection or SuperAIDS) is a condition in which a person with an established human immunodeficiency virus infection acquires a second strain of HIV, often of a different subtype. These can form a recombinant strain that co-exists with the strain from the initial infection, as well from reinfection with a new virus strain, and may cause more rapid disease progression or carry multiple resistances to certain HIV medications.

HIV superinfection may be interclade, where the second infecting virus is phylogenetically distinct from the initial virus, or intraclade, where the two strains are monophyletic.

People with HIV risk superinfection by the same actions that would place a non-infected person at risk of acquiring HIV. These include sharing needles and forgoing condoms with HIV-positive sexual partners. Cases have been reported globally and studies have shown the incidence rate to be 0–7.7% per year. Research from Uganda published in 2012 indicates that HIV superinfection among HIV-infected individuals within a general population remains unknown. Further research indicates that there have been 16 documented cases of superinfection since 2002.

If a person is infected with a second virus before seroconversion to the first virus has taken place, it is termed a dual infection. Infection with a second strain after seroconversion is known as superinfection.