Heat shock protein 90 (Hsp90) plays a critical role in the maintenance of multiple oncogenic pathways and is a required protein for folding and stability of many oncoproteins that are related to the growth, proliferation, and survival of many kinds of cancers. Ganetespib (STA-9090) is a potent, synthetic, small molecule inhibitor of Hsp90, and its binding to Hsp90 is known to result in the degradation of its client proteins and subsequent death of cancer cells. This article provides a review of ganetespib as one of the leading Hsp90 inhibitors, which is under investigation in a broad range of clinical stages for the treatment of cancer.