Stereotaxy is a high-precision technique of radiation therapy used in oncology [1, 2]. Stereotaxy combines the advantages of image guidance and highly conformal and highly hypofractionated radiation dose delivery to treat tumors over a short time. The advent of the gamma knife in the 1950s was the first step toward stereotaxy, and this was aptly termed stereotactic radiosurgery (SRS). Subsequently various organizations have given their definitions, with most limiting the term to treatment deliver within 1–5 fractions. For patients treated with precision technique, but using a higher number of fractions, the term stereotactic radiotherapy (SRT) is used. Cranial stereotaxy paved the way for extracranial stereotaxy that included sites such as the spine, lung, and liver [3]. For extracranial stereotaxy, the terms stereotactic body radiotherapy (SBRT) and stereotactic ablative radiotherapy (SABR) have been used. One of the first clinical experiences was initiated at Karolinska University Hospital, Sweden, in 1991 and was closely followed by Japan in 1994. This technique not only decreased the duration of treatment but also matched the survival rates of surgically treated patients [4, 5]. Over the last few years, there has been a dramatic rise in research as well as practice of stereotaxy (Fig. 19.1).