The Medallion Architecture is a layered data design pattern that organizes lakehouse data into Bronze (raw ingestion), Silver (cleaned and conformed), and Gold (business-ready aggregates) layers to incrementally improve data quality and structure. Originating from Databricks best practices, this pattern has become the de facto standard for modern data lakehouses across platforms like Microsoft Fabric, Snowflake, and AWS, enabling teams to build auditable, scalable data pipelines with clear separation of concerns. The key mental model: each layer represents a progressive refinement contract—Bronze preserves raw truth, Silver enforces cleanliness and standardization, and Gold optimizes for consumption, making data quality improvements explicit and reversible rather than buried in opaque transformation logic.