पेंच (स्क्रू) या बोल्ट एक प्रकार की यांत्रिक युक्ति है जो दो भागों को परस्पर कसने (fastening) के काम आती है। यह किसी धातु के बेलनाकार दण्ड पर वर्तुलाकार (हेलिकल) चूड़ियाँ (थ्रेड्स) काटकर बनायी जाती है।

A screw is an externally helical threaded fastener capable of being tightened or released by a twisting force (torque) to the head. The most common uses of screws are to hold objects together and there are many forms for a variety of materials. Screws might be inserted into holes in assembled parts or a screw may form its own thread. The difference between a screw and a bolt is that the latter is designed to be tightened or released by torquing a nut.