We present a unified framework for understanding the compaction of colloidal gels under their own weight. The dynamics of the collapse are determined by the value of the gravitational stress σg, as compared to the yield stress σY of the network. For σg<σY, gels collapse poroelastically, and their rate of compression decays exponentially in time. For σg>σY, the network eventually yields, leading to rapid settling. In both cases, the rate of collapse is backflow limited, while its overall magnitude is determined by a balance between gravitational stress and network elastic stress. © 2005 The American Physical Society.