Initiation of eukaryotic DNA replication is a tightly controlled process. Replication initiates at multiple specific sites (replication origins) that have been licensed for replication, following the cell cycle-dependent, multi-step assembly of specific factors. Thus, replication origins occur in two chromatin states: a replication-competent pre-replicative (pre-RC) state, when a number of replication proteins assemble on the origin in a stepwise fashion, and a replication-incompetent post-replicative (post-RC) state, in which the origin (or elements of it) is bound only by the origin recognition complex (ORC) (or subunits of it). This review summarizes the origin binding proteins that have been have been identified to date.