Dose-escalated radiation therapy for localized prostate cancer improves disease control but is also associated with worse rectal toxicity. A spacer placed between the prostate and rectum can be used to displace the anterior rectal wall outside of the high-dose radiation regions and potentially minimize radiation-induced rectal toxicity. This systematic review focuses on the published data regarding the different types of commercially available prostate-rectum spacers. Dosimetric results and preliminary clinical data using prostate-rectum spacers in patients with localized prostate cancer treated by curative radiation therapy are compared and discussed.