Custom software (also known as bespoke software) is software that is specially developed for some specific organization or other user. As such, it can be contrasted with the use of software packages developed for the mass market, such as commercial off-the-shelf (COTS) software, or existing free software.

Custom software can be developed by an in-house software development group, or be commissioned from a software house or independent software developer. Since custom software is developed for a single customer it can accommodate that customer's particular preferences and expectations.