GCP Data Pipeline implements the medallion architecture (Bronze-Silver-Gold) using Cloud Composer, Dataflow, and BigQuery to transform raw data into governed, analytics-ready assets. Data flows from diverse sources through Cloud Storage landing zones into Bronze datasets, then through Dataflow transformations and BigQuery routines for deduplication and normalization into Silver, and finally into Gold semantic layers with aggregates and facts. Dataplex provides unified governance, lineage, and catalog across all layers, while Vertex AI and Looker enable downstream analytics and intelligence. This architecture demonstrates enterprise data platform best practices: separation of concerns by maturity tier, infrastructure-as-code via Terraform, security via VPC Service Controls and DLP, and observability through Cloud Logging and Monitoring.