This paper addresses the challenge of governance in pursuit of a genuine and lasting prosperity. Its starting point is to critique the notion that this prosperity is to be found through continued economic growth – even in the richest nations – and to point to a profound dilemma at the heart of the growth debate. Growth may be unsustainable, but degrowth (economic contraction) is unstable. The paper highlights the ways in which this dilemma leads to deep contradictions at the heart of modern governance. The growth-based economy locks government into a particular mode of governing (or “governmentality”) even when this conflicts with government’s own social or environmental goals. This internal conflict explains much of the visceral resistance which politicians and policy makers display towards the growth debate. Conversely, of course, freeing ourselves from the constrictions of growth-based prosperity simultaneously offers the prospect of better governance – a new governmentality for post-growth economics.