Build to Order (BTO: sometimes referred to as Make to Order or Made to Order (MTO)) is a production approach where products are not built until a confirmed order for products is received. Thus, the end consumer determines the time and number of produced products. The ordered product is customized, meeting the design requirements of an individual, organization or business. Such production orders can be generated manually, or through inventory/production management programs. BTO is the oldest style of order fulfillment and is the most appropriate approach used for highly customized or low volume products. Industries with expensive inventory use this production approach. Moreover, "Made to order" products are common in the food service industry, such as at restaurants.

BTO can be considered a Just in Time (JIT) production system, as components or products are only delivered just in time when demanded, in order to reduce wasted time and increase efficiency.