A growing literature explores reasons for rising wealth inequality, but is mostly silent on the role of pension systems despite their well-understood influence on life-cycle savings. This paper develops a simple life-cycle model to lay bare the primary theoretical mechanisms connecting pension systems, asset accumulation, and the wealth distribution. Mandated fully-funded plans transform individuals with lower incomes, often characterized as low savers, into asset owners, and may also imply a more equal wealth distribution than pay-as-you-go-based systems. To test the empirical validity of these predictions, the paper explores a pension reform in Denmark, a country that witnessed declining wealth inequality over the last decades. In a calibrated life-cycle model employing unique register data, the Danish pension reform emerges as a key factor explaining the downward trend in wealth inequality.