Contract review is the highest-volume recurring workload in most corporate legal departments, and standardizing it has become a central concern of the emerging legal operations function. The supporting evidence, however, sits scattered across information systems, business process management, legal informatics, and practitioner literature, and has never been consolidated. This review consolidates it. Searching six databases for work published between January 2010 and June 2021, and following established systematic review guidance, we identified 73 sources and synthesized them thematically. The result is a five-layer taxonomy of contract review standardization covering intake and triage, artifacts, decisions, orchestration, and measurement, whose layers stand in a dependency relation that makes implementation sequence consequential. Reported gains in cycle time, senior counsel capacity, and auditability are consistent across the corpus but weakly evidenced, resting mostly on single-organization accounts without control conditions. The field's binding constraint is measurement: too few studies define contract review cycle time precisely enough for their results to be compared. We propose a common measurement specification, a research agenda, and a staged implementation sequence for practice.