This article gives a concise introduction to the ‘tragedy of the anticommons.’ The anticommons thesis is simple: when too many people own pieces of one thing, nobody can use it. Usually, private ownership creates wealth. But too much ownership has the opposite effect – it leads to wasteful underuse. This is a free market paradox that shows up all across the global economy. If too many owners control a single resource, cooperation breaks down, wealth disappears, and everybody loses. Conceptually, underuse in an anticommons mirrors the familiar problem of overuse in a ‘tragedy of the commons.’ The field of anticommons studies is now well-established. Over a thousand scholars have detailed examples from across the innovation frontier, including drug patenting, telecom licensing, climate change, compulsory land purchase, oil field unitisation, music and art copyright, and post-socialist economic transition. Fixing anticommons tragedy is a key challenge for any legal system committed to innovation and economic growth.