Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various time setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods. Heavy equipment like machine tool beds, ships' propellers, etc. can be cast easily in the required size, rather than fabricating by joining several small pieces. Casting is a 7,000-year-old process. The oldest surviving casting is a copper frog from 3200 BC.

ढलाई (Casting) एक प्रकार की विनिर्माण प्रक्रिया है जो प्राचीन काल से प्रचलित है। इस प्रक्रिया में पिघले हुए धातु, मिश्र धातु, प्लास्टिक अथवा किसी जम सकने वाले द्रव को एक साँचे में डाला जाता है ताकि ठंडा हो जाने पर वह साँचे का आकार ले सके। ठंडा हो जाने के बाद द्रव ठोस हो जाता है और साँचे का आकार ले लेता है। इस ठोस पदार्थ को या तो साँचे से सरका कर अथवा साँचे को तोड़ कर बाहर निकाला जाता है। इस प्रक्रिया को ६००० वर्ष पुराना माना जाता है।