Conventional wisdom suggests that informed investors benefit from trading monopolistically. We show this can fail when investors face uncertainty about liquidity. In a Kyle (1985) framework, we compare profits under monopolistic and competitive equilibria when investors face uncertainty about liquidity trading volatility. While low uncertainty favors coordination, sufficiently high uncertainty reverses this: an individual investor's competitive profits can exceed total monopolistic profits. Endogenizing the collusion decision generates novel predictions: small increases in liquidity uncertainty can cause discrete jumps in trading volume, price volatility, and price informativeness.