Cancer is the most serious disease afflicting humans and a primary cause of death on a global scale. Chemotherapy continues to be one of the most essential cancer treatments, in addition to surgery and radiotherapy. Recently, the use of targeted anticancer medications as an approach for optimizing antitumor therapy has been advocated. One of the most well-established cancer targets are histone deacetylases (HDACs). HDAC inhibitors (HDACis) have evolved as one of the most effective anticancer medications due to their capacity to destroy cancer cells aggressively via alteration of the chromatin structure or inhibition of their activity. Recently, the discovery of selective HDACs has garnered considerable interest not just for their diverse biological activities, but also as potential therapeutic agent with less adverse effects than approved pan inhibitors. This review provides an overview of isoform- and class-selective HDAC inhibitors, including the IC50 values and biological effects on various types of cancer.