Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated (Cas) system (CRISPR-Cas) is a prokaryotic immune system against invading DNA. Today, it is commonly used as a genome editing tool, but it is also a frequent method for treating viral infections. That is possible when a virus has a dsDNA genome or if it replicates through a double-stranded intermediate. Human immunodeficiency virus (HIV) is a retrovirus and its genomic RNA is transcribed into a double-stranded DNA molecule and that is why HIV is a possible target of CRISPR-Cas. With the method, it is possible to treat previously infected cells by introducing Cas9 nuclease and a gRNA molecule with sequence complementarity to HIV into infected cells to attack the proviral DNA. In a second approach, it is possible to introduce Cas9 and gRNA into uninfected cells to await and immediately attack dsDNA that is produced upon a future infection. Treatment of HIV infections has many complications due to the virus' amazing ability to acquire resistance. For this reason, it is recommended to use multiple different therapies at the same time. Even though there are still many obstacles to overcome before CRISPR-Cas could be successfully applied in patients, current research shows incredible potential of the method.