Patent law includes one of this country’s oldest continuous statutory requirements: since 1790, and without variance, inventors are only entitled to patent “new and useful” inventions. While “newness” receives constant attention and debate, usefulness has been largely ignored. Usefulness has transformed into the toothless and misunderstood “utility” doctrine, which requires that patents only have a bare minimum potential for use. This article seeks to reinvent patentable usefulness. It is the first comprehensive look at usefulness and it reasons that a core benefit of the requirement is to aid in the commercialization of inventions. The article then proposes two ways that usefulness can be used to achieve this goal. First, it justifies a current but controversial doctrinal rule: that an invention must have practical usefulness to be patented. Second, it suggests a new rule, that inventions must have commercial usefulness to be patented. Finally, the article concludes with a discussion of the potential costs and benefits of usefulness and discusses future areas of research that would support this article’s proposal.